diff --git a/README.md b/README.md
index ca64337f..42fcdf38 100644
--- a/README.md
+++ b/README.md
@@ -47,6 +47,7 @@ vim.pack.add({
   "https://github.com/nvim-tree/nvim-web-devicons", -- Recommended but not required. Icons in discussion tree.
   "https://github.com/harrisoncramer/gitlab.nvim",
 })
+require("diffview").setup({rename_threshold = 30}) -- Recommended to match the rename threshold of Gitlab
 ---@type GitlabSettings
 local opts = {} -- Your configuration
 require("gitlab").setup(opts)
@@ -60,7 +61,10 @@ With [folke/lazy.nvim](https://github.com/folke/lazy.nvim):
   -- branch = "main", -- Uncomment to use a stable version. The default, possibly unstable, but more actively maintained branch is `develop`.
   dependencies = {
     "MunifTanjim/nui.nvim",
-    "dlyongemallo/diffview-plus.nvim", -- Maintained fork of "sindrets/diffview.nvim".
+    {
+      "dlyongemallo/diffview-plus.nvim", -- Maintained fork of "sindrets/diffview.nvim".
+      opts = { rename_threshold = 30 }, -- Recommended to match the rename threshold of Gitlab
+    },
     "stevearc/dressing.nvim", -- Recommended but not required. Better UI for pickers.
     "nvim-tree/nvim-web-devicons", -- Recommended but not required. Icons in discussion tree.
   },
@@ -77,7 +81,12 @@ And with <a href="https://github.com/lewis6991/pckr.nvim">pckr.nvim</a>:
   -- branch = "main", -- Uncomment to use a stable version. The default, possibly unstable, but more actively maintained branch is `develop`.
   requires = {
     "MunifTanjim/nui.nvim",
-    "dlyongemallo/diffview-plus.nvim", -- Maintained fork of "sindrets/diffview.nvim".
+    {
+      "dlyongemallo/diffview-plus.nvim", -- Maintained fork of "sindrets/diffview.nvim".
+      config = function()
+        require("diffview").setup({ rename_threshold = 30 }) -- Recommended to match the rename threshold of Gitlab
+      end,
+    },
     "stevearc/dressing.nvim", -- Recommended but not required. Better UI for pickers.
     "nvim-tree/nvim-web-devicons", -- Recommended but not required. Icons in discussion tree.
   },
diff --git a/cmd/app/comment_helpers.go b/cmd/app/comment_helpers.go
index 05881da2..0ab1893e 100644
--- a/cmd/app/comment_helpers.go
+++ b/cmd/app/comment_helpers.go
@@ -7,8 +7,18 @@ import (
 	gitlab "gitlab.com/gitlab-org/api/client-go"
 )
 
-/* LinePosition represents a position in a line range. Unlike the Gitlab struct, this does not contain LineCode with a sha1 of the filename */
-type LinePosition struct {
+/* PositionInfo represents one endpoint (start or end) of a line range, as sent by the Lua
+* plugin. Unlike the Gitlab struct, it has no LineCode - Lua can't compute a sha1, so
+* buildCommentPosition computes one below from OldLine and NewLine.
+*
+* OldLine and NewLine are always real, non-nil integers, even when Type is "old" or "new"
+* and only one side actually has a line. On the side that doesn't, the value is a position
+* marker, not a claim that a line exists there: it's wherever that side's cursor was
+* sitting when the other side's line was found. LineCode is always built from this
+* unzeroed pair; buildCommentPosition separately zeroes the inapplicable side before
+* setting it on the request's LineRange.{Start,End}.{OldLine,NewLine} - see
+* zeroInapplicableLine. */
+type PositionInfo struct {
 	Type    string `json:"type"`
 	OldLine int64  `json:"old_line"`
 	NewLine int64  `json:"new_line"`
@@ -16,8 +26,8 @@ type LinePosition struct {
 
 /* LineRange represents the range of a note. */
 type LineRange struct {
-	StartRange *LinePosition `json:"start"`
-	EndRange   *LinePosition `json:"end"`
+	Start *PositionInfo `json:"start" validate:"required"`
+	End   *PositionInfo `json:"end" validate:"required"`
 }
 
 /* PositionData represents the position of a comment or note (relative to a file diff) */
@@ -30,7 +40,7 @@ type PositionData struct {
 	BaseCommitSHA  string     `json:"base_commit_sha"`
 	StartCommitSHA string     `json:"start_commit_sha"`
 	Type           string     `json:"type"`
-	LineRange      *LineRange `json:"line_range,omitempty"`
+	LineRange      *LineRange `json:"line_range" validate:"required_with=FileName"`
 }
 
 /* RequestWithPosition is an interface that abstracts the handling of position data for a comment or a draft comment */
@@ -59,31 +69,54 @@ func buildCommentPosition(commentWithPositionData RequestWithPosition) *gitlab.P
 		OldLine:      positionData.OldLine,
 	}
 
-	if positionData.LineRange != nil {
-		shaFormat := "%x_%d_%d"
-		startFilenameSha := fmt.Sprintf(
-			shaFormat,
-			sha1.Sum([]byte(positionData.FileName)),
-			positionData.LineRange.StartRange.OldLine,
-			positionData.LineRange.StartRange.NewLine,
-		)
-		endFilenameSha := fmt.Sprintf(
-			shaFormat,
-			sha1.Sum([]byte(positionData.FileName)),
-			positionData.LineRange.EndRange.OldLine,
-			positionData.LineRange.EndRange.NewLine,
-		)
-		opt.LineRange = &gitlab.LineRangeOptions{
-			Start: &gitlab.LinePositionOptions{
-				Type:     &positionData.LineRange.StartRange.Type,
-				LineCode: &startFilenameSha,
-			},
-			End: &gitlab.LinePositionOptions{
-				Type:     &positionData.LineRange.EndRange.Type,
-				LineCode: &endFilenameSha,
-			},
-		}
+	shaFormat := "%x_%d_%d"
+	startFilenameSha := fmt.Sprintf(
+		shaFormat,
+		sha1.Sum([]byte(positionData.FileName)),
+		positionData.LineRange.Start.OldLine,
+		positionData.LineRange.Start.NewLine,
+	)
+	endFilenameSha := fmt.Sprintf(
+		shaFormat,
+		sha1.Sum([]byte(positionData.FileName)),
+		positionData.LineRange.End.OldLine,
+		positionData.LineRange.End.NewLine,
+	)
+
+	startOldLine, startNewLine := zeroInapplicableLine(positionData.LineRange.Start)
+	endOldLine, endNewLine := zeroInapplicableLine(positionData.LineRange.End)
+
+	opt.LineRange = &gitlab.LineRangeOptions{
+		Start: &gitlab.LinePositionOptions{
+			Type:     &positionData.LineRange.Start.Type,
+			LineCode: &startFilenameSha,
+			OldLine:  &startOldLine,
+			NewLine:  &startNewLine,
+		},
+		End: &gitlab.LinePositionOptions{
+			Type:     &positionData.LineRange.End.Type,
+			LineCode: &endFilenameSha,
+			OldLine:  &endOldLine,
+			NewLine:  &endNewLine,
+		},
 	}
 
 	return opt
 }
+
+/* zeroInapplicableLine returns a line_range endpoint's OldLine/NewLine with the side
+* that its Type doesn't apply to zeroed out: NewLine for a deleted ("old") line, OldLine
+* for an added ("new") line. Both stay real for an unmodified ("") or "expanded" line.
+* The unzeroed pair is still what the LineCode hash above is computed from - Gitlab
+* expects LineCode to encode the real old/new correspondence even when the displayed
+* OldLine or NewLine is zeroed. */
+func zeroInapplicableLine(position *PositionInfo) (oldLine int64, newLine int64) {
+	oldLine, newLine = position.OldLine, position.NewLine
+	switch position.Type {
+	case "old":
+		newLine = 0
+	case "new":
+		oldLine = 0
+	}
+	return oldLine, newLine
+}
diff --git a/cmd/app/comment_helpers_test.go b/cmd/app/comment_helpers_test.go
new file mode 100644
index 00000000..50f0cefe
--- /dev/null
+++ b/cmd/app/comment_helpers_test.go
@@ -0,0 +1,65 @@
+package app
+
+import (
+	"testing"
+)
+
+func TestBuildCommentPosition(t *testing.T) {
+	makePositionData := func(startType string, startOld, startNew int64, endType string, endOld, endNew int64) PositionData {
+		return PositionData{
+			FileName:       "file.txt",
+			HeadCommitSHA:  "head-sha",
+			BaseCommitSHA:  "base-sha",
+			StartCommitSHA: "start-sha",
+			Type:           "text",
+			LineRange: &LineRange{
+				Start: &PositionInfo{Type: startType, OldLine: startOld, NewLine: startNew},
+				End:   &PositionInfo{Type: endType, OldLine: endOld, NewLine: endNew},
+			},
+		}
+	}
+
+	t.Run("zeroes NewLine for a deleted (\"old\") line, keeping LineCode's real pair", func(t *testing.T) {
+		positionData := makePositionData("", 4, 4, "old", 5, 5)
+		opt := buildCommentPosition(CommentWithPosition{PositionData: positionData})
+
+		assert(t, *opt.LineRange.End.OldLine, int64(5))
+		assert(t, *opt.LineRange.End.NewLine, int64(0))
+		assert(t, *opt.LineRange.End.LineCode, "5436437fa01a7d3e41d46741da54b451446774ca_5_5")
+	})
+
+	t.Run("zeroes OldLine for an added (\"new\") line, keeping LineCode's real pair", func(t *testing.T) {
+		positionData := makePositionData("", 4, 4, "new", 5, 5)
+		opt := buildCommentPosition(CommentWithPosition{PositionData: positionData})
+
+		assert(t, *opt.LineRange.End.OldLine, int64(0))
+		assert(t, *opt.LineRange.End.NewLine, int64(5))
+		assert(t, *opt.LineRange.End.LineCode, "5436437fa01a7d3e41d46741da54b451446774ca_5_5")
+	})
+
+	t.Run("keeps both lines real for an unmodified (\"\") line", func(t *testing.T) {
+		positionData := makePositionData("", 4, 4, "", 5, 6)
+		opt := buildCommentPosition(CommentWithPosition{PositionData: positionData})
+
+		assert(t, *opt.LineRange.End.OldLine, int64(5))
+		assert(t, *opt.LineRange.End.NewLine, int64(6))
+	})
+
+	t.Run("keeps both lines real for an expanded line", func(t *testing.T) {
+		positionData := makePositionData("", 4, 4, "expanded", 59, 61)
+		opt := buildCommentPosition(CommentWithPosition{PositionData: positionData})
+
+		assert(t, *opt.LineRange.End.OldLine, int64(59))
+		assert(t, *opt.LineRange.End.NewLine, int64(61))
+	})
+
+	t.Run("zeroes the start and end independently", func(t *testing.T) {
+		positionData := makePositionData("new", 0, 50, "", 60, 62)
+		opt := buildCommentPosition(CommentWithPosition{PositionData: positionData})
+
+		assert(t, *opt.LineRange.Start.OldLine, int64(0))
+		assert(t, *opt.LineRange.Start.NewLine, int64(50))
+		assert(t, *opt.LineRange.End.OldLine, int64(60))
+		assert(t, *opt.LineRange.End.NewLine, int64(62))
+	})
+}
diff --git a/cmd/app/comment_test.go b/cmd/app/comment_test.go
index a10ef5fc..947eb359 100644
--- a/cmd/app/comment_test.go
+++ b/cmd/app/comment_test.go
@@ -59,6 +59,10 @@ func TestPostComment(t *testing.T) {
 			Comment: "Some comment",
 			PositionData: PositionData{
 				FileName: "file.txt",
+				LineRange: &LineRange{
+					Start: &PositionInfo{Type: "", OldLine: 4, NewLine: 4},
+					End:   &PositionInfo{Type: "", OldLine: 4, NewLine: 4},
+				},
 			},
 		}
 		request := makeRequest(t, http.MethodPost, "/mr/comment", testCommentCreationData)
diff --git a/cmd/app/middleware_test.go b/cmd/app/middleware_test.go
index 598c3d59..e3291522 100644
--- a/cmd/app/middleware_test.go
+++ b/cmd/app/middleware_test.go
@@ -111,4 +111,39 @@ func TestValidatorMiddleware(t *testing.T) {
 		), request)
 		assert(t, data.Message, "Some message")
 	})
+	t.Run("Should reject a line_range with a missing endpoint instead of panicking", func(t *testing.T) {
+		payload := PostCommentRequest{
+			Comment: "Some comment",
+			PositionData: PositionData{
+				FileName:  "file.txt",
+				LineRange: &LineRange{}, // Start and End left nil
+			},
+		}
+		request := makeRequest(t, http.MethodPost, "/mr/comment", payload)
+		svc := middleware(
+			commentService{testProjectData, fakeCommentClient{}},
+			withMr(testProjectData, fakeMergeRequestLister{}),
+			withPayloadValidation(methodToPayload{http.MethodPost: newPayload[PostCommentRequest]}),
+			withMethodCheck(http.MethodPost),
+		)
+		data, status := getFailData(t, svc, request)
+		assert(t, data.Message, "Invalid payload")
+		assert(t, data.Details, "Start is required; End is required")
+		assert(t, status, http.StatusBadRequest)
+	})
+	t.Run("Should allow a missing line_range when there is no FileName (unlinked comment)", func(t *testing.T) {
+		payload := PostCommentRequest{
+			Comment: "Some comment",
+			// PositionData is left zero-valued: no FileName, no LineRange.
+		}
+		request := makeRequest(t, http.MethodPost, "/mr/comment", payload)
+		svc := middleware(
+			commentService{testProjectData, fakeCommentClient{}},
+			withMr(testProjectData, fakeMergeRequestLister{}),
+			withPayloadValidation(methodToPayload{http.MethodPost: newPayload[PostCommentRequest]}),
+			withMethodCheck(http.MethodPost),
+		)
+		data := getSuccessData(t, svc, request)
+		assert(t, data.Message, "Comment created successfully")
+	})
 }
diff --git a/doc/gitlab.nvim.txt b/doc/gitlab.nvim.txt
index 1868e5df..3ee038f9 100644
--- a/doc/gitlab.nvim.txt
+++ b/doc/gitlab.nvim.txt
@@ -85,6 +85,7 @@ With |vim.pack| (the built-in plugin manager on Neovim 0.12 and newer):
     "https://github.com/nvim-tree/nvim-web-devicons", -- Recommended but not required. Icons in discussion tree.
     "https://github.com/harrisoncramer/gitlab.nvim",
   })
+  require("diffview").setup({rename_threshold = 30}) -- Recommended to match the rename threshold of Gitlab
   ---@type GitlabSettings
   local opts = {} -- Your configuration
   require("gitlab").setup(opts)
@@ -97,7 +98,10 @@ With folke/lazy.nvim:
     -- branch = "main", -- Uncomment to use a stable version. The default, possibly unstable, but more actively maintained branch is `develop`.
     dependencies = {
       "MunifTanjim/nui.nvim",
-      "dlyongemallo/diffview-plus.nvim", -- Maintained fork of "sindrets/diffview.nvim".
+      {
+        "dlyongemallo/diffview-plus.nvim", -- Maintained fork of "sindrets/diffview.nvim".
+        opts = { rename_threshold = 30 }, -- Recommended to match the rename threshold of Gitlab
+      },
       "stevearc/dressing.nvim", -- Recommended but not required. Better UI for pickers.
       "nvim-tree/nvim-web-devicons", -- Recommended but not required. Icons in discussion tree.
     },
@@ -112,7 +116,12 @@ And with pckr.nvim:
     -- branch = "main", -- Uncomment to use a stable version. The default, possibly unstable, but more actively maintained branch is `develop`.
     requires = {
       "MunifTanjim/nui.nvim",
-      "dlyongemallo/diffview-plus.nvim", -- Maintained fork of "sindrets/diffview.nvim".
+      {
+        "dlyongemallo/diffview-plus.nvim", -- Maintained fork of "sindrets/diffview.nvim".
+        config = function()
+          require("diffview").setup({ rename_threshold = 30 }) -- Recommended to match the rename threshold of Gitlab
+        end,
+      },
       "stevearc/dressing.nvim", -- Recommended but not required. Better UI for pickers.
       "nvim-tree/nvim-web-devicons", -- Recommended but not required. Icons in discussion tree.
     },
diff --git a/lua/gitlab/actions/comment.lua b/lua/gitlab/actions/comment.lua
index 862521af..dc3a1e3b 100644
--- a/lua/gitlab/actions/comment.lua
+++ b/lua/gitlab/actions/comment.lua
@@ -8,6 +8,7 @@ local job = require("gitlab.job")
 local u = require("gitlab.utils")
 local popup = require("gitlab.popup")
 local git = require("gitlab.git")
+local hunks = require("gitlab.hunks")
 local discussions = require("gitlab.actions.discussions")
 local draft_notes = require("gitlab.actions.draft_notes")
 local miscellaneous = require("gitlab.actions.miscellaneous")
@@ -21,6 +22,19 @@ local M = {
   comment_popup = nil,
 }
 
+---Build a Location from the live reviewer state (the active Diffview session).
+---Return nil when the location cannot be built due to missing reviewer data.
+---@return Location?
+M.new_location_from_reviewer = function()
+  local reviewer_data = reviewer.get_reviewer_data()
+  if reviewer_data == nil then
+    return nil
+  end
+  local diff_hunks =
+    hunks.get_hunks(reviewer_data.old_sha, reviewer_data.new_sha, reviewer_data.old_file_name, reviewer_data.file_name)
+  return Location.new(reviewer_data, diff_hunks)
+end
+
 ---Fire the API to send the comment data to the Go server.
 ---@param text string comment text
 ---@param unlinked boolean if true, the comment is not linked to a line
@@ -151,11 +165,11 @@ M.create_comment_layout = function(opts)
     title = "Note"
     user_settings = popup_settings.note
   else
-    local file_name = (M.location.reviewer_data.new_sha_focused or M.location.reviewer_data.old_file_name == "")
+    local file_name = (M.location.reviewer_data.new_file_focused or M.location.reviewer_data.old_file_name == "")
         and M.location.reviewer_data.file_name
       or M.location.reviewer_data.old_file_name
     title =
-      popup.create_title("Comment", file_name, M.location.visual_range.start_line, M.location.visual_range.end_line)
+      popup.create_title("Comment", file_name, M.location.reviewer_data.start_line, M.location.reviewer_data.end_line)
     user_settings = popup_settings.comment
   end
   local settings = u.merge(popup_settings, user_settings or {})
@@ -207,7 +221,7 @@ end
 ---Open a comment popup in order to create a comment on the changed/updated line in the
 ---current MR.
 M.create_comment = function()
-  M.location = Location.new()
+  M.location = M.new_location_from_reviewer()
   if not M.can_create_comment(false) then
     return
   end
@@ -219,7 +233,7 @@ end
 ---Open a multi-line comment popup in order to create a multi-line comment on the
 ---changed/updated line in the current MR.
 M.create_multiline_comment = function()
-  M.location = Location.new()
+  M.location = M.new_location_from_reviewer()
   if not M.can_create_comment(true) then
     u.press_escape()
     return
@@ -238,12 +252,12 @@ end
 
 ---Given the current visually selected area of text, builds text to fill in the
 ---comment popup with a suggested change
----@return LineRange?
+---@return string[]?
 local build_suggestion = function()
   local current_line = vim.api.nvim_win_get_cursor(0)[1]
-  local range_length = M.location.visual_range.end_line - M.location.visual_range.start_line
+  local range_length = M.location.reviewer_data.end_line - M.location.reviewer_data.start_line
   local backticks = "```"
-  local selected_lines = u.get_lines(M.location.visual_range.start_line, M.location.visual_range.end_line)
+  local selected_lines = u.get_lines(M.location.reviewer_data.start_line, M.location.reviewer_data.end_line)
 
   for _, line in ipairs(selected_lines) do
     if string.match(line, "^```%S*$") then
@@ -253,9 +267,9 @@ local build_suggestion = function()
   end
 
   local suggestion_start
-  if M.location.visual_range.start_line == current_line then
+  if M.location.reviewer_data.start_line == current_line then
     suggestion_start = backticks .. "suggestion:-0+" .. range_length
-  elseif M.location.visual_range.end_line == current_line then
+  elseif M.location.reviewer_data.end_line == current_line then
     suggestion_start = backticks .. "suggestion:-" .. range_length .. "+0"
   else
     --- This should never happen afaik
@@ -274,7 +288,7 @@ end
 ---Open a popup to create a suggestion comment on the changed/updated line in the current MR
 ---See: https://docs.gitlab.com/ee/user/project/merge_requests/reviews/suggestions.html
 M.create_comment_suggestion = function()
-  M.location = Location.new()
+  M.location = M.new_location_from_reviewer()
   if not M.can_create_comment(true) then
     u.press_escape()
     return
@@ -355,7 +369,7 @@ M.can_create_comment = function(must_be_visual)
     return false
   end
 
-  if M.location == nil or M.location.location_data == nil then
+  if M.location == nil then
     u.notify("Error getting location information", vim.log.levels.ERROR)
     return false
   end
diff --git a/lua/gitlab/actions/common.lua b/lua/gitlab/actions/common.lua
index ff346332..03ca63a0 100644
--- a/lua/gitlab/actions/common.lua
+++ b/lua/gitlab/actions/common.lua
@@ -267,6 +267,7 @@ M.get_line_numbers_for_range = function(old_line, new_line, start_line_code, end
   elseif new_line ~= nil then
     local range = new_end_line - new_start_line
     -- Force start_line to be greater than 0
+    -- TODO: use `math.max(new_line - range, 1)` instead
     local start_line = (new_line - range > 0) and (new_line - range) or 1
     return start_line, new_line, true
   else
diff --git a/lua/gitlab/actions/discussions/init.lua b/lua/gitlab/actions/discussions/init.lua
index c3600f7d..81e23247 100644
--- a/lua/gitlab/actions/discussions/init.lua
+++ b/lua/gitlab/actions/discussions/init.lua
@@ -25,9 +25,9 @@ local emoji = require("gitlab.emoji")
 local M = {
   split_visible = false,
   split = nil,
-  ---@type number
+  ---@type integer
   linked_bufnr = nil,
-  ---@type number
+  ---@type integer
   unlinked_bufnr = nil,
   ---@type NuiTree?
   discussion_tree = nil,
@@ -36,7 +36,7 @@ local M = {
 }
 
 ---Delete discussion buffers to prevent leaked buffers on each M.open/M.close cycle.
----@param split_bufnr number? Passed in because `unmount` has already nil'd `M.split.bufnr`.
+---@param split_bufnr integer? Passed in because `unmount` has already nil'd `M.split.bufnr`.
 local function delete_bufs(split_bufnr)
   -- pairs, because any of these might be nil
   for _, bufnr in pairs({ split_bufnr, M.linked_bufnr, M.unlinked_bufnr }) do
diff --git a/lua/gitlab/annotations.lua b/lua/gitlab/annotations.lua
index 7aee76cf..7d66129c 100644
--- a/lua/gitlab/annotations.lua
+++ b/lua/gitlab/annotations.lua
@@ -11,13 +11,22 @@
 ---@field avatar_url string
 ---@field web_url string
 
----@class LinePosition
----@field line_code string
----@field type string
+---The modification of a line in a diff.
+---@alias ModificationType
+---| "old" A deleted line
+---| "new" An added line
+---| "" An unmodified line adjacent to a hunk
+---| "expanded" A line more than 3 lines away from any change (i.e. one that Gitlab only shows upon manually expanding the diff)
+
+---@class PositionInfo
+---@field line_code? string SHA of the file name with old and new line numbers, e.g., 3f454a98e586d1aa0d322e19afd5e67e08f2d3c8_1_1
+---@field old_line integer The corresponding line in the old version of the file. For added lines it is the line after the last common unchanged line
+---@field new_line integer The corresponding line in the new version of the file. For deleted lines it is the line after the last common unchanged line
+---@field type ModificationType
 
----@class GitlabLineRange
----@field start LinePosition
----@field end LinePosition
+---@class LineRange
+---@field start PositionInfo
+---@field end PositionInfo
 
 ---@class NotePosition
 ---@field base_sha string
@@ -28,7 +37,7 @@
 ---@field new_line integer?
 ---@field old_path string?
 ---@field old_line integer?
----@field line_range GitlabLineRange?
+---@field line_range LineRange?
 
 ---@class Note
 ---@field id integer
@@ -98,21 +107,14 @@
 ---@field lnum number
 ---@field buffer number?
 
----@class LineRange
+---@class ReviewerData
+---@field old_file_name string
+---@field file_name string
+---@field old_sha string
+---@field new_sha string
 ---@field start_line integer
 ---@field end_line integer
-
----@class DiffviewInfo
----@field modification_type string
----@field file_name string
----Relevant for renamed files only, the name of the file in the previous commit
----@field old_file_name string
----@field current_bufnr integer
----@field opposite_bufnr integer
----@field new_line_from_buf integer
----@field old_line_from_buf integer
----@field new_sha_focused boolean
----@field current_win_id integer
+---@field new_file_focused boolean
 
 ---@class DraftNote
 ---@field note string
diff --git a/lua/gitlab/git.lua b/lua/gitlab/git.lua
index d3a5bb42..a37e8073 100644
--- a/lua/gitlab/git.lua
+++ b/lua/gitlab/git.lua
@@ -8,7 +8,7 @@ local M = {}
 ---@return string? result The result of the command as a string. Nil if the command failed
 ---@return string? error The error the command failed with. Nil if the command succeeded
 local run_system = function(command)
-  local result = vim.fn.trim(vim.fn.system(command))
+  local result = vim.fn.trim(vim.fn.system(command), "\r\n")
   if vim.v.shell_error ~= 0 then
     require("gitlab.utils").notify(result, vim.log.levels.ERROR)
     return nil, result
@@ -241,21 +241,27 @@ M.check_mr_in_good_condition = function()
   end
 end
 
----Return the full diff between the local working tree relative to the named `base_sha`,
----for the given file(s).
----@param base_sha string Base SHA to diff against
+---Return the diff between two commits for the given file(s).
+---Diffs the two commit trees directly rather than against the working tree, so it's
+---correct regardless of what's currently checked out.
+---@param old_sha string SHA to diff from
+---@param new_sha string SHA to diff to
 ---@param old_path? string Old file name
 ---@param new_path? string New file name - relevant for renamed files, ignored if same as old_path
 ---@return string? diff, string? err
-M.diff_files = function(base_sha, old_path, new_path)
+M.diff_files = function(old_sha, new_sha, old_path, new_path)
   return run_system({
     "git",
+    "-c",
+    "diff.suppressBlankEmpty=false",
     "diff",
     "--minimal",
-    "--unified=0",
+    "--find-renames=30%",
+    "--unified=3",
     "--no-color",
     "--no-ext-diff",
-    base_sha,
+    old_sha,
+    new_sha,
     "--",
     old_path,
     new_path,
diff --git a/lua/gitlab/hunks.lua b/lua/gitlab/hunks.lua
index 046502bd..7d532de4 100644
--- a/lua/gitlab/hunks.lua
+++ b/lua/gitlab/hunks.lua
@@ -1,7 +1,3 @@
-local List = require("gitlab.utils.list")
-local u = require("gitlab.utils")
-local state = require("gitlab.state")
-
 local M = {}
 
 ---@class Hunk
@@ -9,24 +5,22 @@ local M = {}
 ---@field old_range integer
 ---@field new_line integer
 ---@field new_range integer
+---@field lines? string[] The hunk's body lines: context, added, and removed; prefixed with " ", "+", and "-", respectively.
 
----@class HunksAndDiff
----@field hunks Hunk[] List of hunks
----@field all_diff_output string[] The data from the git diff command
-
----Parse hunk header line into a Lua table. Return nil, if line is not a hunk header.
+---Parse a diff line into a Lua table if it's a hunk header, otherwise return nil.
 ---@param line string
 ---@return Hunk?
 M.parse_possible_hunk_headers = function(line)
-  if line:sub(1, 2) == "@@" then
+  if line:match("^@@") then
     -- match:
     --  @@ -23 +23 @@ ...
     --  @@ -23,0 +23 @@ ...
     --  @@ -41,0 +42,4 @@ ...
     local old_start, old_range, new_start, new_range = line:match("@@+ %-(%d+),?(%d*) %+(%d+),?(%d*) @@+")
 
-    -- Git omits the ",N" count when it is exactly 1, so an empty capture means 1,
-    -- while a captured "0" means a genuine zero-length range (pure insertion/deletion).
+    -- The unified diff format omits the ",N" count when it is exactly 1, so an empty
+    -- capture means 1, while a captured "0" means a genuine zero-length range (pure
+    -- insertion/deletion).
     return {
       old_line = tonumber(old_start),
       old_range = tonumber(old_range) or 1,
@@ -36,249 +30,88 @@ M.parse_possible_hunk_headers = function(line)
   end
 end
 
----Return true if given line was removed in the MR.
----The diff comes from `git.diff_files`, which runs with `--unified=0`. A hunk
----therefore carries no context lines and its old range holds removed lines only,
----so membership in that range already answers the question.
----@param linenr integer Line number in the old version of the file
----@param hunk Hunk A hunk candidate from the file's diff
----@return boolean
-local line_was_removed = function(linenr, hunk)
-  return linenr >= hunk.old_line and linenr < hunk.old_line + hunk.old_range
-end
-
----Return true if given line was added in the MR.
----@param linenr integer Line number in the new version of the file
----@param hunk Hunk A hunk candidate from the file's diff
----@param all_diff_output string[]
----@return boolean
-local line_was_added = function(linenr, hunk, all_diff_output)
-  for matching_line_index, line in ipairs(all_diff_output) do
-    local found_hunk = M.parse_possible_hunk_headers(line)
-    if found_hunk ~= nil and vim.deep_equal(found_hunk, hunk) then
-      -- Parse the lines from the hunk and return only the added lines
-      local hunk_lines = {}
-      local i = 1
-      local line_content = all_diff_output[matching_line_index + i]
-      while line_content ~= nil and line_content:sub(1, 2) ~= "@@" do
-        if string.match(line_content, "^%+") then
-          table.insert(hunk_lines, line_content)
-        end
-        i = i + 1
-        line_content = all_diff_output[matching_line_index + i]
-      end
-
-      -- We are only looking at added lines in the changed hunk to see if their index
-      -- matches the index of a line that was added
-      local starting_index = found_hunk.new_line - 1 -- The "+j" will add one
-      for j, _ in ipairs(hunk_lines) do
-        if (starting_index + j) == linenr then
-          return true
-        end
-      end
-    end
-  end
-  return false
-end
-
----Parse the diff of the current file against the base SHA of the MR.
----@param base_sha string Git base SHA of the merge request
----@return HunksAndDiff hunks_and_diff The hunk headers and full diff of the file
-local parse_hunks_and_diff = function(base_sha)
+---Parse the diff between two commits for a file into a list of hunks.
+---Each hunk carries its own header info and body lines.
+---@param old_sha string SHA to diff from
+---@param new_sha string SHA to diff to
+---@param old_path string Old file name
+---@param new_path string New file name
+---@return Hunk[] hunks
+M.get_hunks = function(old_sha, new_sha, old_path, new_path)
   local hunks = {}
-  local all_diff_output = {}
 
   local git = require("gitlab.git")
-  local reviewer = require("gitlab.reviewer")
-
-  local diff, _ = git.diff_files(base_sha, reviewer.get_current_file_oldpath(), reviewer.get_current_file_path())
-  if diff ~= nil then
-    for line in diff:gmatch("[^\r\n]+") do
-      table.insert(all_diff_output, line)
-      local hunk = M.parse_possible_hunk_headers(line)
-      if hunk ~= nil then
-        table.insert(hunks, hunk)
-      end
-    end
+  local diff, _ = git.diff_files(old_sha, new_sha, old_path, new_path)
+  if diff == nil then
+    return hunks
   end
 
-  return { hunks = hunks, all_diff_output = all_diff_output }
-end
-
----Parse the lines from a diff and return the index of the next hunk, when provided an
----initial index.
----@param lines string[]
----@param i integer
----@return integer?
-local next_hunk_index = function(lines, i)
-  for j, line in ipairs(lines) do
+  local current_hunk = nil
+  for line in diff:gmatch("[^\r\n]+") do
     local hunk = M.parse_possible_hunk_headers(line)
-    if hunk ~= nil and j > i then
-      return j
-    end
-  end
-  return nil
-end
-
----Process the number of changes until the target is reached.
----This returns a negative or positive number indicating the number of lines in
----the hunk that have been added or removed prior to the target line.
----@param linenr integer
----@param hunk Hunk
----@param lines string[]
----@return integer
-local net_changed_in_hunk_before_line = function(linenr, hunk, lines)
-  local net_lines = 0
-  local current_line_old = hunk.old_line
-
-  for _, line in ipairs(lines) do
-    if line:sub(1, 1) == "-" then
-      if current_line_old < linenr then
-        net_lines = net_lines - 1
-      end
-      current_line_old = current_line_old + 1
-    elseif line:sub(1, 1) == "+" then
-      if current_line_old < linenr then
-        net_lines = net_lines + 1
+    if hunk ~= nil then
+      hunk.lines = {}
+      table.insert(hunks, hunk)
+      current_hunk = hunk
+    elseif current_hunk ~= nil then
+      local prefix = line:sub(1, 1)
+      if prefix == " " or prefix == "+" or prefix == "-" then
+        table.insert(current_hunk.lines, line)
       end
-    else
-      current_line_old = current_line_old + 1
-    end
-  end
-
-  return net_lines
-end
-
----Count the total number of changes in a set of lines, positive if added lines and
----negative if removed lines.
----@param lines string[]
----@return integer
-local count_changes = function(lines)
-  local total = 0
-  for _, line in ipairs(lines) do
-    if line:match("^%+") then
-      total = total + 1
-    else
-      total = total - 1
     end
   end
-  return total
-end
 
----Return the modification type for the selected line.
----@param new_line? integer The starting or ending line of the current selection in the new version
----@param hunks Hunk[]
----@param all_diff_output string[]
----@return ("added"|"bad_file_unmodified")?
-local function get_modification_type_from_new_sha(new_line, hunks, all_diff_output)
-  if new_line == nil then
-    return nil
-  end
-  return List.new(hunks):find(function(hunk)
-    local new_line_end = hunk.new_line + hunk.new_range - (hunk.new_range > 0 and 1 or 0)
-    local in_new_range = new_line >= hunk.new_line and new_line <= new_line_end
-    local is_range_zero = hunk.new_range == 0 and hunk.old_range == 0
-    return in_new_range and (is_range_zero or line_was_added(new_line, hunk, all_diff_output))
-  end) and "added" or "bad_file_unmodified"
+  return hunks
 end
 
----Return the modification type for the selected line.
----@param old_line? integer The starting or ending line of the current selection in the old version
----@param new_line? integer The starting or ending line of the current selection in the new version
+---Return the line position (old_line, new_line, type) for a queried line number.
+---Walk the hunk list once. Callers use this for both the start and end of a line range.
 ---@param hunks Hunk[]
----@return ("deleted"|"unmodified")?
-local function get_modification_type_from_old_sha(old_line, new_line, hunks)
-  if old_line == nil then
-    return nil
-  end
-
-  return List.new(hunks):find(function(hunk)
-    local old_line_end = hunk.old_line + hunk.old_range - (hunk.old_range > 0 and 1 or 0)
-    local new_line_end = hunk.new_line + hunk.new_range - (hunk.new_range > 0 and 1 or 0)
-    local in_old_range = old_line >= hunk.old_line and old_line <= old_line_end
-    local in_new_range = new_line >= hunk.new_line and new_line <= new_line_end
-    return (in_old_range or in_new_range) and line_was_removed(old_line, hunk)
-  end) and "deleted" or "unmodified"
-end
-
----Return the modification type of the line for which the comment is created.
----This is in order to build the payload for Gitlab correctly by setting the old line
----and new line.
----FIXME: This misses the fact that Gitlab also uses the type "expanded" (when
----commenting on lines that are more than 3 lines away from any change, thus are on
----folded lines that the user expanded manually).
----FIXME: This function is called three times when creating a ranged comment - this
----means three `git diff` calls, six times parsing the same diff output. This should
----only be done once!
----@param old_line? integer
----@param new_line? integer
----@param new_sha_focused boolean
----@return ("added"|"bad_file_unmodified"|"deleted"|"unmodified")?
-function M.get_modification_type(old_line, new_line, new_sha_focused)
-  local hunk_and_diff_data = parse_hunks_and_diff(state.INFO.diff_refs.base_sha)
-  if hunk_and_diff_data.hunks == nil then
-    return
-  end
-
-  local hunks = hunk_and_diff_data.hunks
-  local all_diff_output = hunk_and_diff_data.all_diff_output
-  return new_sha_focused and get_modification_type_from_new_sha(new_line, hunks, all_diff_output)
-    or get_modification_type_from_old_sha(old_line, new_line, hunks)
-end
-
----Return the matching line number of a line in the new/old version of the file compared
----to the currently selected version.
----@param old_sha string The base SHA of the MR when getting matching line in the old version, otherwise the head SHA when getting matching line in the new version
----@param new_sha string The head SHA of the MR when getting matching line in the old version, otherwise the base SHA when getting matching line in the new version
----@param file_path string The file name after change
----@param old_file_path string The file name before change (different from file_path for renamed/moved files)
----@param linenr integer The starting or ending line of the current selection
----@return integer?
-M.calculate_matching_line_new = function(old_sha, new_sha, file_path, old_file_path, linenr)
-  local net_change = 0
-  local diff_cmd = string.format(
-    "git diff --minimal --unified=0 --no-color %s %s -- %s %s",
-    old_sha,
-    new_sha,
-    old_file_path,
-    file_path
-  )
-
-  local handle = io.popen(diff_cmd)
-  if handle == nil then
-    u.notify(string.format("Error running git diff command for %s", file_path), vim.log.levels.ERROR)
-    return nil
-  end
-
-  local all_lines = List.new({})
-  for line in handle:lines() do
-    table.insert(all_lines, line)
-  end
-
-  for i, line in ipairs(all_lines) do
-    local hunk = M.parse_possible_hunk_headers(line)
-    if hunk ~= nil then
-      if linenr <= hunk.old_line then
-        -- We have reached a hunk which starts after our target, return the changed total lines
-        return linenr + net_change
-      end
-
-      local n = next_hunk_index(all_lines, i) or #all_lines
-      local diff_lines = all_lines:slice(i + 1, n - 1)
-
-      -- If the line is IN the hunk, process the hunk and return the change until that line
-      if linenr >= hunk.old_line and linenr < hunk.old_line + hunk.old_range then
-        net_change = linenr + net_change + net_changed_in_hunk_before_line(linenr, hunk, diff_lines)
-        return net_change
+---@param linenr integer Line number on the focused side
+---@param new_file_focused boolean Whether linenr is a line number in the new version of the file
+---@return PositionInfo
+M.get_line_position = function(hunks, linenr, new_file_focused)
+  local net_change_before = 0
+
+  for _, hunk in ipairs(hunks) do
+    local hunk_start = new_file_focused and hunk.new_line or hunk.old_line
+    local hunk_end = new_file_focused and (hunk.new_line + hunk.new_range - 1) or (hunk.old_line + hunk.old_range - 1)
+
+    -- Inside the hunk
+    if linenr >= hunk_start and linenr <= hunk_end then
+      local old_cursor, new_cursor = hunk.old_line, hunk.new_line
+      for _, line in ipairs(hunk.lines) do
+        local prefix = line:sub(1, 1)
+        if prefix == " " then
+          if (new_file_focused and new_cursor == linenr) or (not new_file_focused and old_cursor == linenr) then
+            return { old_line = old_cursor, new_line = new_cursor, type = "" }
+          end
+          old_cursor, new_cursor = old_cursor + 1, new_cursor + 1
+        elseif prefix == "-" then
+          if not new_file_focused and old_cursor == linenr then
+            return { old_line = old_cursor, new_line = new_cursor, type = "old" }
+          end
+          old_cursor = old_cursor + 1
+        elseif prefix == "+" then
+          if new_file_focused and new_cursor == linenr then
+            return { old_line = old_cursor, new_line = new_cursor, type = "new" }
+          end
+          new_cursor = new_cursor + 1
+        end
       end
-
-      -- If it's not it's after this hunk, just add all the changes and keep iterating
-      net_change = net_change + count_changes(diff_lines)
+    -- Past the hunk
+    elseif linenr > hunk_end then
+      net_change_before = net_change_before + (hunk.new_range - hunk.old_range)
     end
   end
 
-  -- TODO: Possibly handle lines that are out of range in the new files
-  return linenr + net_change + 1
+  -- When linenr falls outside every hunk (including each hunk's 3-line context, since
+  -- M.get_hunks fetches the diff with --unified=3) the cursor was in unmodified content
+  -- that Gitlab collapses - the type is "expanded".
+  if new_file_focused then
+    return { old_line = linenr - net_change_before, new_line = linenr, type = "expanded" }
+  end
+  return { old_line = linenr, new_line = linenr + net_change_before, type = "expanded" }
 end
 
 return M
diff --git a/lua/gitlab/indicators/common.lua b/lua/gitlab/indicators/common.lua
index 649b13d1..5324a463 100644
--- a/lua/gitlab/indicators/common.lua
+++ b/lua/gitlab/indicators/common.lua
@@ -70,6 +70,11 @@ end
 M.is_old_sha = function(d_or_n)
   local position = M.get_first_note(d_or_n).position
   local old_start_line = position.line_range ~= nil and M.parse_line_code(position.line_range.start.line_code) or nil
+  -- FIXME: Update how `old_start_line ~= 0` is evaluated. After the Location refactor,
+  -- the numbers in line codes never are set to 0, but we should support the old way of
+  -- determining "is_old_sha" at least for some time because users will encounter the
+  -- old values in existing discussion nodes created with the old version of the plugin.
+  -- This should also check if the type of the range location(s) is "old".
   return position.old_line ~= nil and old_start_line ~= 0
 end
 
diff --git a/lua/gitlab/reviewer/init.lua b/lua/gitlab/reviewer/init.lua
index 0336bf4b..3037cf67 100644
--- a/lua/gitlab/reviewer/init.lua
+++ b/lua/gitlab/reviewer/init.lua
@@ -6,7 +6,6 @@
 local List = require("gitlab.utils.list")
 local u = require("gitlab.utils")
 local state = require("gitlab.state")
-local hunks = require("gitlab.hunks")
 local async = require("diffview.async")
 
 local M = {
@@ -34,6 +33,14 @@ M.open = function()
   require("gitlab.git_async").check_current_branch_up_to_date_on_remote()
   local git = require("gitlab.git")
 
+  -- TODO: The rename threshold used by Gitlab (through Gitaly) is 30%, see
+  -- https://gitlab.com/gitlab-org/gitaly/-/blob/db39e26f8f8a8da62e2c2db00325cf51315c89db/internal/gitaly/service/diff/commit_diff.go#L64-64
+  -- https://gitlab.com/gitlab-org/gitaly/-/blob/0e81e24ae1f650c242670eb7bf66c4b4b91b7813/internal/gitaly/service/diff/find_changed_paths.go#L116-116
+  -- dlyongemallo/diffview.nvim can be configured to respect this:
+  -- require("diffview.config").get_config({rename_threshold = 30})
+  -- But a preferable solution would be to be able to specify the value per Diffview
+  -- command (issue: https://github.com/dlyongemallo/diffview-plus.nvim/issues/301).
+
   local diffview_open_command = "DiffviewOpen"
 
   if state.settings.reviewer_settings.diffview.imply_local then
@@ -172,66 +179,44 @@ M.jump = function(file_name, old_file_name, linenr, new_buffer)
   vim.cmd("normal! zz")
 end
 
----Get the data from diffview, such as line information and file name.
----To be used by other modules such as the comment module to create line codes or set
----diagnostics.
----@param current_win integer The ID of the currently focused window
----@return DiffviewInfo?
-M.get_reviewer_data = function(current_win)
-  if M.diffview == nil then
-    return
-  end
-  local old_win = u.get_window_id_by_buffer_id(M.diffview_layout.a.file.bufnr)
-  local new_win = u.get_window_id_by_buffer_id(M.diffview_layout.b.file.bufnr)
-
-  if old_win == nil or new_win == nil then
-    u.notify("Error getting window IDs for current files", vim.log.levels.ERROR)
-    return
-  end
-
-  local current_file = M.get_current_file_path()
-  if current_file == nil then
-    u.notify("Error getting current file from Diffview", vim.log.levels.ERROR)
-    return
+---Return start line and end line of visual selection.
+---@return integer
+---@return integer
+local get_visual_selection_boundaries = function()
+  local start_line = vim.fn.line("v")
+  local end_line = vim.fn.line(".")
+  if start_line > end_line then
+    start_line, end_line = end_line, start_line
   end
+  return start_line, end_line
+end
 
-  local new_line = vim.api.nvim_win_get_cursor(new_win)[1]
-  local old_line = vim.api.nvim_win_get_cursor(old_win)[1]
-
-  local new_sha_focused = M.is_new_sha_focused(current_win)
-
-  local modification_type = hunks.get_modification_type(old_line, new_line, new_sha_focused)
-  if modification_type == nil then
-    u.notify("Error getting modification type", vim.log.levels.ERROR)
+---Get the data from the reviewer: file names, line information, and cursor focus.
+---@return ReviewerData?
+M.get_reviewer_data = function()
+  if M.diffview_layout == nil then
     return
   end
 
-  -- FIXME: This causes false positive warnings when the selection range spans a
-  -- modified line but the new_line itself is on an unmodified line.
-  if modification_type == "bad_file_unmodified" then
-    u.notify("Comments on unmodified lines will be placed in the old file", vim.log.levels.WARN)
-  end
-
-  local current_bufnr = new_sha_focused and M.diffview_layout.b.file.bufnr or M.diffview_layout.a.file.bufnr
-  local opposite_bufnr = new_sha_focused and M.diffview_layout.a.file.bufnr or M.diffview_layout.b.file.bufnr
+  local start_line, end_line = get_visual_selection_boundaries()
+  local new_file_focused = M.is_new_file_focused(vim.api.nvim_get_current_win())
+  local diff_refs = state.INFO.diff_refs
 
   return {
-    old_file_name = M.is_file_renamed() and M.diffview_layout.a.file.path or "",
+    old_file_name = M.is_file_renamed() and M.diffview_layout.a.file.path or M.diffview_layout.b.file.path,
     file_name = M.diffview_layout.b.file.path,
-    old_line_from_buf = old_line,
-    new_line_from_buf = new_line,
-    modification_type = modification_type,
-    current_bufnr = current_bufnr,
-    opposite_bufnr = opposite_bufnr,
-    new_sha_focused = new_sha_focused,
-    current_win_id = current_win,
+    old_sha = diff_refs.base_sha,
+    new_sha = diff_refs.head_sha,
+    start_line = start_line,
+    end_line = end_line,
+    new_file_focused = new_file_focused,
   }
 end
 
 ---Return true if user is focused on the new version of the file, otherwise false.
 ---@param current_win integer The ID of the currently focused window
 ---@return boolean
-M.is_new_sha_focused = function(current_win)
+M.is_new_file_focused = function(current_win)
   local b_win = u.get_window_id_by_buffer_id(M.diffview_layout.b.file.bufnr)
   local a_win = u.get_window_id_by_buffer_id(M.diffview_layout.a.file.bufnr)
   if a_win ~= current_win and b_win ~= current_win then
diff --git a/lua/gitlab/reviewer/location.lua b/lua/gitlab/reviewer/location.lua
index 87d65172..725fc104 100755
--- a/lua/gitlab/reviewer/location.lua
+++ b/lua/gitlab/reviewer/location.lua
@@ -1,243 +1,54 @@
-local u = require("gitlab.utils")
 local hunks = require("gitlab.hunks")
-local state = require("gitlab.state")
-
----@class ReviewerLineInfo
----@field old_line? integer
----@field new_line? integer
----@field type "new"|"old"
-
----@class ReviewerRangeInfo
----@field start ReviewerLineInfo
----@field end ReviewerLineInfo
 
 ---@class LocationData
 ---@field old_line? integer
 ---@field new_line? integer
----@field line_range? ReviewerRangeInfo
+---@field line_range? LineRange
 
 ---@class Location
 ---@field location_data LocationData
----@field reviewer_data DiffviewInfo
----@field run function
----@field build_location_data function
----@field visual_range table
+---@field reviewer_data ReviewerData
+---@field new fun(reviewer_data: ReviewerData, diff_hunks: Hunk[]): Location
+---@field build_location_data fun()
 
 local Location = {}
 Location.__index = Location
 
----Return information about the selection in the reviewer.
----Return nil when the location cannot be created due to missing reviewer data.
----@return Location?
-function Location.new()
-  local current_win = vim.api.nvim_get_current_win()
-  local reviewer_data = require("gitlab.reviewer").get_reviewer_data(current_win)
-  if reviewer_data == nil then
-    return nil
-  end
-  local location = {}
-  local instance = setmetatable(location, Location)
+---Build a Location from already-resolved reviewer data and diff hunks.
+---@param reviewer_data ReviewerData
+---@param diff_hunks Hunk[]
+---@return Location
+function Location.new(reviewer_data, diff_hunks)
+  local instance = setmetatable({}, Location)
   instance.reviewer_data = reviewer_data
-  instance.base_sha = state.INFO.diff_refs.base_sha
-  instance.head_sha = state.INFO.diff_refs.head_sha
-  instance:build_location_data()
+  instance:build_location_data(diff_hunks)
   return instance
 end
 
----Build the payload for creating a comment based on the file name, modification type of
----the diff, and line numbers.
-function Location:build_location_data()
-  ---@type DiffviewInfo
-  local reviewer_data = self.reviewer_data
-
-  local start_line, end_line = u.get_visual_selection_boundaries()
-  ---@type LineRange
-  self.visual_range = { start_line = start_line, end_line = end_line }
-
+---Build the payload for creating a comment.
+---@param diff_hunks Hunk[]
+function Location:build_location_data(diff_hunks)
+  local line_range = {
+    start = hunks.get_line_position(diff_hunks, self.reviewer_data.start_line, self.reviewer_data.new_file_focused),
+    ["end"] = hunks.get_line_position(diff_hunks, self.reviewer_data.end_line, self.reviewer_data.new_file_focused),
+  }
   ---@type LocationData
   self.location_data = {
-    old_line = nil,
-    new_line = nil,
-    line_range = nil,
-  }
-
-  -- Comment on new line: Include only new_line in payload.
-  -- Comment on deleted line: Include only old_line in payload.
-  -- The line was not found in any hunks, send both lines.
-  if reviewer_data.modification_type == "added" then
-    self.location_data.old_line = nil
-    self.location_data.new_line = reviewer_data.new_line_from_buf
-  elseif reviewer_data.modification_type == "deleted" then
-    self.location_data.old_line = reviewer_data.old_line_from_buf
-    self.location_data.new_line = nil
-  elseif
-    reviewer_data.modification_type == "unmodified" or reviewer_data.modification_type == "bad_file_unmodified"
-  then
-    self.location_data.old_line = reviewer_data.old_line_from_buf
-    self.location_data.new_line = reviewer_data.new_line_from_buf
-  end
-
-  -- TODO: Don't skip line_range for single-line comments (Gitlab doesn't skip them either).
-  if end_line > start_line then
-    self.location_data.line_range = {
-      start = {},
-      ["end"] = {},
-    }
-  else
-    return
-  end
-
-  self:set_range_start()
-  self:set_range_end()
-
-  -- Ranged comments should always use the end of the range.
-  -- Otherwise they will not highlight the full comment in Gitlab.
-  self.location_data.old_line = self.location_data.line_range["end"].old_line
-  self.location_data.new_line = self.location_data.line_range["end"].new_line
-end
-
--- Helper methods 🤝
-
----Return the matching line number from the new version of the file.
----For instance, line 12 in the new version may be scroll-linked to line 10 in the old
----version.
----@param linenr integer The starting or ending line of the current selection
----@return integer?
-function Location:get_line_number_from_new_sha(linenr)
-  if self.reviewer_data.new_sha_focused then
-    return linenr
-  end
-  -- Otherwise we want to get the matching line in the opposite buffer
-  return hunks.calculate_matching_line_new(
-    self.base_sha,
-    self.head_sha,
-    self.reviewer_data.file_name,
-    self.reviewer_data.old_file_name,
-    linenr
-  )
-end
-
----Return the matching line number from the old version of the file.
----For instance, line 12 in the new version may be scroll-linked to line 10 in the old
----version.
----@param linenr integer The starting or ending line of the current selection
----@return integer?
-function Location:get_line_number_from_old_sha(linenr)
-  if not self.reviewer_data.new_sha_focused then
-    return linenr
-  end
-
-  -- Otherwise we want to get the matching line in the opposite buffer
-  return hunks.calculate_matching_line_new(
-    self.head_sha,
-    self.base_sha,
-    self.reviewer_data.file_name,
-    self.reviewer_data.old_file_name,
-    linenr
-  )
-end
-
----Return the current line number from whatever version (new or old) the reviewer is
----focused in.
----@return integer?
-function Location:get_current_line()
-  if self.reviewer_data.current_win_id == nil then
-    return
-  end
-
-  local current_line = vim.api.nvim_win_get_cursor(self.reviewer_data.current_win_id)[1]
-  return current_line
-end
-
----Set the range start to the location_data for the Gitlab payload based on the
----modification type, visual selection range, and the hunk data.
-function Location:set_range_start()
-  local current_file = require("gitlab.reviewer").get_current_file_path()
-  if current_file == nil then
-    u.notify("Error getting current file from Diffview", vim.log.levels.ERROR)
-    return
-  end
-
-  if self.reviewer_data.current_win_id == nil then
-    u.notify("Error getting window number of SHA for start of range", vim.log.levels.ERROR)
-    return
-  end
-
-  local current_line = self:get_current_line()
-  if current_line == nil then
-    u.notify("Error getting current line for start of range", vim.log.levels.ERROR)
-    return
-  end
-
-  local new_line = self:get_line_number_from_new_sha(self.visual_range.start_line)
-  local old_line = self:get_line_number_from_old_sha(self.visual_range.start_line)
-  if
-    (new_line == nil and self.reviewer_data.modification_type ~= "deleted")
-    or (old_line == nil and self.reviewer_data.modification_type ~= "added")
-  then
-    u.notify("Error getting new or old line for start of range", vim.log.levels.ERROR)
-    return
-  end
-
-  local modification_type = hunks.get_modification_type(old_line, new_line, self.reviewer_data.new_sha_focused)
-  if modification_type == nil then
-    u.notify("Error getting modification type for start of range", vim.log.levels.ERROR)
-    return
-  end
-
-  self.location_data.line_range.start = {
-    new_line = modification_type ~= "deleted" and new_line or nil,
-    old_line = modification_type ~= "added" and old_line or nil,
-    -- FIXME: The type should only be "old" explicitly for comments on deleted lines.
-    -- For unchanged lines this should be empty. Apart from that, the modification type
-    -- can also be "expanded" (when commenting on lines that are more than 3 lines away
-    -- from any change, thus are on folded lines that the user expanded manually.
-    type = modification_type == "added" and "new" or "old",
-  }
-end
-
----Set the range end to the location_data for the Gitlab payload based on the
----modification type, visual selection range, and the hunk data.
-function Location:set_range_end()
-  local current_file = require("gitlab.reviewer").get_current_file_path()
-  if current_file == nil then
-    u.notify("Error getting current file from Diffview", vim.log.levels.ERROR)
-    return
-  end
-
-  if self.reviewer_data.current_win_id == nil then
-    u.notify("Error getting window number of SHA for end of range", vim.log.levels.ERROR)
-    return
-  end
-
-  local current_line = self:get_current_line()
-  if current_line == nil then
-    u.notify("Error getting current line for end of range", vim.log.levels.ERROR)
-    return
-  end
-
-  local new_line = self:get_line_number_from_new_sha(self.visual_range.end_line)
-  local old_line = self:get_line_number_from_old_sha(self.visual_range.end_line)
-
-  if
-    (new_line == nil and self.reviewer_data.modification_type ~= "deleted")
-    or (old_line == nil and self.reviewer_data.modification_type ~= "added")
-  then
-    u.notify("Error getting new or old line for end of range", vim.log.levels.ERROR)
-    return
-  end
-
-  local modification_type = hunks.get_modification_type(old_line, new_line, self.reviewer_data.new_sha_focused)
-  if modification_type == nil then
-    u.notify("Error getting modification type for end of range", vim.log.levels.ERROR)
-    return
-  end
-
-  self.location_data.line_range["end"] = {
-    new_line = modification_type ~= "deleted" and new_line or nil,
-    old_line = modification_type ~= "added" and old_line or nil,
-    type = modification_type == "added" and "new" or "old",
+    -- Top-level old_line and new_line must correspond to the end of the range to be
+    -- placed correctly in Gitlab. They are only set if they match the modification
+    -- type.
+    old_line = line_range["end"].type ~= "new" and line_range["end"].old_line or nil,
+    new_line = line_range["end"].type ~= "old" and line_range["end"].new_line or nil,
+    line_range = line_range,
   }
+  -- TODO: Warn the user when position.type == "" (unmodified) while their selection was
+  -- made on the "wrong" side, since gitlab.nvim may render such a comment's diagnostic
+  -- on the other side of the diff than the one the user was looking at. This used to
+  -- exist (see the removed "bad_file_unmodified" modification type) but was lost in a
+  -- refactor; reviving it needs its own design, since which side gitlab.nvim actually
+  -- picks incorrectly doesn't reflect the start of the comment range and can show a
+  -- comment spanning "new-unchanged" lines on the old file even if it belongs to the
+  -- new file.
 end
 
 return Location
diff --git a/lua/gitlab/utils/init.lua b/lua/gitlab/utils/init.lua
index 366a097c..56c08a22 100644
--- a/lua/gitlab/utils/init.lua
+++ b/lua/gitlab/utils/init.lua
@@ -557,19 +557,6 @@ M.check_visual_mode = function()
   return true
 end
 
----Return start line and end line of visual selection.
----TODO: Move to `lua/gitlab/reviewer/location.lua`
----@return integer
----@return integer
-M.get_visual_selection_boundaries = function()
-  local start_line = vim.fn.line("v")
-  local end_line = vim.fn.line(".")
-  if start_line > end_line then
-    start_line, end_line = end_line, start_line
-  end
-  return start_line, end_line
-end
-
 ---Get icon for filename if nvim-web-devicons plugin is available, otherwise return
 ---empty string.
 ---@return string?
diff --git a/tests/spec/comment_spec.lua b/tests/spec/comment_spec.lua
new file mode 100644
index 00000000..2d06992d
--- /dev/null
+++ b/tests/spec/comment_spec.lua
@@ -0,0 +1,59 @@
+describe("gitlab/actions/comment.lua", function()
+  describe("new_location_from_reviewer", function()
+    -- comment.lua captures `reviewer` via a top-level require, so stubbing
+    -- gitlab.reviewer only takes effect if comment.lua is required again afterwards.
+    local function load_comment()
+      package.loaded["gitlab.actions.comment"] = nil
+      return require("gitlab.actions.comment")
+    end
+
+    after_each(function()
+      package.loaded["gitlab.reviewer"] = nil
+      package.loaded["gitlab.git"] = nil
+      package.loaded["gitlab.actions.comment"] = nil
+    end)
+
+    it("returns nil when the reviewer has no data to give", function()
+      package.loaded["gitlab.reviewer"] = {
+        get_reviewer_data = function()
+          return nil
+        end,
+      }
+
+      local comment = load_comment()
+      assert.is_nil(comment.new_location_from_reviewer())
+    end)
+
+    it("threads reviewer_data's shas and file names into hunks.get_hunks in the right order", function()
+      package.loaded["gitlab.reviewer"] = {
+        get_reviewer_data = function()
+          return {
+            old_file_name = "old_name.txt",
+            file_name = "new_name.txt",
+            old_sha = "old-sha",
+            new_sha = "new-sha",
+            start_line = 1,
+            end_line = 1,
+            new_file_focused = true,
+          }
+        end,
+      }
+
+      local seen_old_sha, seen_new_sha, seen_old_path, seen_new_path
+      package.loaded["gitlab.git"] = {
+        diff_files = function(old_sha, new_sha, old_path, new_path)
+          seen_old_sha, seen_new_sha, seen_old_path, seen_new_path = old_sha, new_sha, old_path, new_path
+          return nil, nil
+        end,
+      }
+
+      local comment = load_comment()
+      comment.new_location_from_reviewer()
+
+      assert.are.same("old-sha", seen_old_sha)
+      assert.are.same("new-sha", seen_new_sha)
+      assert.are.same("old_name.txt", seen_old_path)
+      assert.are.same("new_name.txt", seen_new_path)
+    end)
+  end)
+end)
diff --git a/tests/spec/hunks_spec.lua b/tests/spec/hunks_spec.lua
index 4195ed73..eb8c0527 100644
--- a/tests/spec/hunks_spec.lua
+++ b/tests/spec/hunks_spec.lua
@@ -27,103 +27,142 @@ describe("gitlab/hunks.lua", function()
     end)
   end)
 
-  describe("get_modification_type", function()
-    local state = require("gitlab.state")
-
+  describe("get_hunks", function()
     local function stub_diff(diff_text)
       package.loaded["gitlab.git"] = {
         diff_files = function()
           return diff_text, nil
         end,
       }
-      package.loaded["gitlab.reviewer"] = {
-        get_current_file_oldpath = function()
-          return "file.txt"
-        end,
-        get_current_file_path = function()
-          return "file.txt"
-        end,
-      }
     end
 
-    before_each(function()
-      state.INFO = { diff_refs = { base_sha = "base-sha" } }
-    end)
-
     after_each(function()
-      state.INFO = nil
       package.loaded["gitlab.git"] = nil
-      package.loaded["gitlab.reviewer"] = nil
     end)
 
-    it("does not classify the unmodified context line above a single-line deletion as added", function()
+    it("attaches each hunk's own body lines instead of a flat diff blob", function()
       stub_diff([[
 diff --git a/file.txt b/file.txt
 index 1111111..2222222 100644
 --- a/file.txt
 +++ b/file.txt
-@@ -5 +4,0 @@
--old content that was removed
+@@ -2,7 +2,6 @@
+ line 2
+ line 3
+ line 4
+-line 5
+ line 6
+ line 7
+ line 8
 ]])
 
-      local got = hunks.get_modification_type(4, 4, true)
-      assert.are_not.same("added", got)
-      assert.are.same("bad_file_unmodified", got)
+      local got = hunks.get_hunks("old-sha", "new-sha", "file.txt", "file.txt")
+      assert.are.same(1, #got)
+      assert.are.same({ old_line = 2, old_range = 7, new_line = 2, new_range = 6 }, {
+        old_line = got[1].old_line,
+        old_range = got[1].old_range,
+        new_line = got[1].new_line,
+        new_range = got[1].new_range,
+      })
+      assert.are.same({ " line 2", " line 3", " line 4", "-line 5", " line 6", " line 7", " line 8" }, got[1].lines)
     end)
 
-    it("keeps classifying the context line above a two-line deletion as bad_file_unmodified", function()
+    it("splits body lines into separate hunks when the diff has more than one", function()
       stub_diff([[
 diff --git a/file.txt b/file.txt
 index 1111111..2222222 100644
 --- a/file.txt
 +++ b/file.txt
-@@ -5,2 +4,0 @@
--old line 5
--old line 6
+@@ -2,4 +2,4 @@
+ line 2
+-line 3
++line three
+ line 4
+@@ -40,3 +40,4 @@
+ line 40
++line 41
+ line 42
 ]])
 
-      local got = hunks.get_modification_type(4, 4, true)
-      assert.are.same("bad_file_unmodified", got)
+      local got = hunks.get_hunks("old-sha", "base-sha", "file.txt", "file.txt")
+      assert.are.same(2, #got)
+      assert.are.same({ " line 2", "-line 3", "+line three", " line 4" }, got[1].lines)
+      assert.are.same({ " line 40", "+line 41", " line 42" }, got[2].lines)
     end)
 
-    it("treats a deleted line as deleted", function()
-      stub_diff([[
-diff --git a/file.txt b/file.txt
-index 1111111..2222222 100644
---- a/file.txt
-+++ b/file.txt
-@@ -5 +4,0 @@
--old line 5
-]])
+    it("returns no hunks when there is no diff", function()
+      stub_diff(nil)
+      local got = hunks.get_hunks("old-sha", "base-sha", "file.txt", "file.txt")
+      assert.are.same({}, got)
+    end)
+  end)
+
+  describe("get_line_position", function()
+    it("classifies a deleted line and shifts the unmodified lines that follow it", function()
+      local hunk = {
+        old_line = 2,
+        old_range = 7,
+        new_line = 2,
+        new_range = 6,
+        lines = { " a", " b", " c", "-removed", " d", " e", " f" },
+      }
 
-      assert.are.same("deleted", hunks.get_modification_type(5, 4, false))
+      assert.are.same({ old_line = 5, new_line = 5, type = "old" }, hunks.get_line_position({ hunk }, 5, false))
+      assert.are.same({ old_line = 6, new_line = 5, type = "" }, hunks.get_line_position({ hunk }, 6, false))
+      assert.are.same({ old_line = 6, new_line = 5, type = "" }, hunks.get_line_position({ hunk }, 5, true))
     end)
 
-    it("treats the line below a single-line deletion as unmodified", function()
-      stub_diff([[
-diff --git a/file.txt b/file.txt
-index 1111111..2222222 100644
---- a/file.txt
-+++ b/file.txt
-@@ -5 +4,0 @@
--old line 5
-]])
+    it("classifies an added line and shifts the unmodified lines that follow it", function()
+      local hunk = {
+        old_line = 2,
+        old_range = 6,
+        new_line = 2,
+        new_range = 7,
+        lines = { " a", " b", " c", "+added", " d", " e", " f" },
+      }
 
-      assert.are.same("unmodified", hunks.get_modification_type(6, 5, false))
+      assert.are.same({ old_line = 5, new_line = 5, type = "new" }, hunks.get_line_position({ hunk }, 5, true))
+      assert.are.same({ old_line = 5, new_line = 6, type = "" }, hunks.get_line_position({ hunk }, 5, false))
     end)
 
-    it("treats the line below a multi-line deletion as unmodified", function()
-      stub_diff([[
-diff --git a/file.txt b/file.txt
-index 1111111..2222222 100644
---- a/file.txt
-+++ b/file.txt
-@@ -5,2 +4,0 @@
--old line 5
--old line 6
-]])
+    it("treats a line beyond any hunk's context as expanded, shifted by earlier hunks", function()
+      local hunks_list = {
+        { old_line = 2, old_range = 2, new_line = 2, new_range = 5, lines = { " a", "+b", "+c", " d", "+e" } },
+      }
+
+      -- net change introduced by the hunk: new_range(5) - old_range(2) = +3
+      assert.are.same(
+        { old_line = 50, new_line = 53, type = "expanded" },
+        hunks.get_line_position(hunks_list, 50, false)
+      )
+      assert.are.same(
+        { old_line = 47, new_line = 50, type = "expanded" },
+        hunks.get_line_position(hunks_list, 50, true)
+      )
+    end)
+
+    it("treats a line before any hunk as expanded with no shift", function()
+      local hunks_list = {
+        { old_line = 20, old_range = 1, new_line = 20, new_range = 0, lines = { "-x" } },
+      }
+
+      assert.are.same({ old_line = 5, new_line = 5, type = "expanded" }, hunks.get_line_position(hunks_list, 5, false))
+    end)
+
+    it("treats a line between two distant hunks as expanded, shifted only by the earlier one", function()
+      local hunks_list = {
+        { old_line = 2, old_range = 2, new_line = 2, new_range = 5, lines = { " a", "+b", "+c", " d", "+e" } },
+        { old_line = 100, old_range = 5, new_line = 103, new_range = 3, lines = { " a", "-b", "-c", " d", " e" } },
+      }
+
+      assert.are.same(
+        { old_line = 50, new_line = 53, type = "expanded" },
+        hunks.get_line_position(hunks_list, 50, false)
+      )
+    end)
 
-      assert.are.same("unmodified", hunks.get_modification_type(7, 5, false))
+    it("returns an empty hunk list result as expanded with no shift", function()
+      assert.are.same({ old_line = 10, new_line = 10, type = "expanded" }, hunks.get_line_position({}, 10, false))
     end)
   end)
 end)
diff --git a/tests/spec/location_spec.lua b/tests/spec/location_spec.lua
new file mode 100644
index 00000000..cb660806
--- /dev/null
+++ b/tests/spec/location_spec.lua
@@ -0,0 +1,104 @@
+local hunks = require("gitlab.hunks")
+local Location = require("gitlab.reviewer.location")
+
+describe("gitlab/reviewer/location.lua", function()
+  local function hunks_from_diff(diff_text)
+    package.loaded["gitlab.git"] = {
+      diff_files = function()
+        return diff_text, nil
+      end,
+    }
+    local file_hunks = hunks.get_hunks("old-sha", "new-sha", "file.txt", "file.txt")
+    package.loaded["gitlab.git"] = nil
+    return file_hunks
+  end
+
+  local function reviewer_data(overrides)
+    return vim.tbl_extend("force", {
+      old_file_name = "file.txt",
+      file_name = "file.txt",
+      old_sha = "old-sha",
+      new_sha = "new-sha",
+      start_line = 1,
+      end_line = 1,
+      new_file_focused = true,
+    }, overrides or {})
+  end
+
+  -- A single-line deletion at old line 5, surrounded by --unified=3 context (old 2-8, new 2-7).
+  -- Each context line is labeled "old new" so the expected shift is visible in the fixture itself.
+  local DELETION_HUNKS = hunks_from_diff([[
+diff --git a/file.txt b/file.txt
+index 1111111..2222222 100644
+--- a/file.txt
++++ b/file.txt
+@@ -2,7 +2,6 @@
+ line 2 2
+ line 3 3
+ line 4 4
+-line 5
+ line 6 5
+ line 7 6
+ line 8 7
+]])
+
+  -- A single-line insertion after old line 4, surrounded by --unified=3 context (old 2-7, new 2-8).
+  -- Each context line is labeled "old new" so the expected shift is visible in the fixture itself.
+  local ADDITION_HUNKS = hunks_from_diff([[
+diff --git a/file.txt b/file.txt
+index 1111111..2222222 100644
+--- a/file.txt
++++ b/file.txt
+@@ -2,6 +2,7 @@
+ line 2 2
+ line 3 3
+ line 4 4
++line   5
+ line 5 6
+ line 6 7
+ line 7 8
+]])
+
+  it("builds a range on unmodified lines with real, matching old/new line numbers", function()
+    local location =
+      Location.new(reviewer_data({ start_line = 2, end_line = 4, new_file_focused = true }), DELETION_HUNKS)
+
+    assert.are.same({ old_line = 2, new_line = 2, type = "" }, location.location_data.line_range.start)
+    assert.are.same({ old_line = 4, new_line = 4, type = "" }, location.location_data.line_range["end"])
+    assert.are.same(4, location.location_data.old_line)
+    assert.are.same(4, location.location_data.new_line)
+  end)
+
+  it("nils out the top-level old_line when the range ends on an added line", function()
+    -- new-side selection from unmodified line 2 to the added line (new_line 5)
+    local location =
+      Location.new(reviewer_data({ start_line = 2, end_line = 5, new_file_focused = true }), ADDITION_HUNKS)
+
+    assert.are.same({ old_line = 2, new_line = 2, type = "" }, location.location_data.line_range.start)
+    assert.are.same({ old_line = 5, new_line = 5, type = "new" }, location.location_data.line_range["end"])
+    assert.is_nil(location.location_data.old_line)
+    assert.are.same(5, location.location_data.new_line)
+  end)
+
+  it("nils out the top-level new_line when the range ends on a deleted line", function()
+    -- old-side selection from unmodified line 2 to the deleted line (old_line 5)
+    local location =
+      Location.new(reviewer_data({ start_line = 2, end_line = 5, new_file_focused = false }), DELETION_HUNKS)
+
+    assert.are.same({ old_line = 2, new_line = 2, type = "" }, location.location_data.line_range.start)
+    assert.are.same({ old_line = 5, new_line = 5, type = "old" }, location.location_data.line_range["end"])
+    assert.are.same(5, location.location_data.old_line)
+    assert.is_nil(location.location_data.new_line)
+  end)
+
+  it("keeps both top-level line numbers real for an expanded (far-from-any-change) range", function()
+    -- Line 500 is nowhere near the hunk (old 2-8 / new 2-7), so it falls outside every
+    -- hunk's --unified=3 context and is classified as "expanded", not "".
+    local location =
+      Location.new(reviewer_data({ start_line = 500, end_line = 500, new_file_focused = false }), DELETION_HUNKS)
+
+    assert.are.same({ old_line = 500, new_line = 499, type = "expanded" }, location.location_data.line_range["end"])
+    assert.are.same(500, location.location_data.old_line)
+    assert.are.same(499, location.location_data.new_line)
+  end)
+end)