diff --git a/resources/celerity/map.php b/resources/celerity/map.php
index c09dd3e94b..1364cbf183 100644
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -10,8 +10,8 @@ return array(
     'core.pkg.css' => '6408f2d3',
     'core.pkg.js' => '5a1c336d',
     'darkconsole.pkg.js' => '8ab24e01',
-    'differential.pkg.css' => 'df94a9e2',
-    'differential.pkg.js' => 'f458a7dc',
+    'differential.pkg.css' => '5f5d3a4c',
+    'differential.pkg.js' => '58dae818',
     'diffusion.pkg.css' => '591664fa',
     'diffusion.pkg.js' => 'bfc0737b',
     'maniphest.pkg.css' => '68d4dd3d',
@@ -55,7 +55,7 @@ return array(
     'rsrc/css/application/dashboard/dashboard.css' => '17937d22',
     'rsrc/css/application/diff/inline-comment-summary.css' => 'eb5f8e8c',
     'rsrc/css/application/differential/add-comment.css' => 'c478bcaa',
-    'rsrc/css/application/differential/changeset-view.css' => '88100552',
+    'rsrc/css/application/differential/changeset-view.css' => 'f9011399',
     'rsrc/css/application/differential/core.css' => '7ac3cabc',
     'rsrc/css/application/differential/results-table.css' => '181aa9d9',
     'rsrc/css/application/differential/revision-comment.css' => '48186045',
@@ -367,7 +367,7 @@ return array(
     'rsrc/js/application/differential/behavior-comment-preview.js' => '6932def3',
     'rsrc/js/application/differential/behavior-diff-radios.js' => 'e1ff79b1',
     'rsrc/js/application/differential/behavior-dropdown-menus.js' => '2035b9cb',
-    'rsrc/js/application/differential/behavior-edit-inline-comments.js' => '33d4c5e2',
+    'rsrc/js/application/differential/behavior-edit-inline-comments.js' => '334267b3',
     'rsrc/js/application/differential/behavior-keyboard-nav.js' => '2c426492',
     'rsrc/js/application/differential/behavior-populate.js' => '8694b1df',
     'rsrc/js/application/differential/behavior-show-field-details.js' => 'bba9eedf',
@@ -518,7 +518,7 @@ return array(
     'conpherence-notification-css' => '04a6e10a',
     'conpherence-update-css' => '1099a660',
     'conpherence-widget-pane-css' => '3d575438',
-    'differential-changeset-view-css' => '88100552',
+    'differential-changeset-view-css' => 'f9011399',
     'differential-core-view-css' => '7ac3cabc',
     'differential-inline-comment-editor' => '41060c54',
     'differential-results-table-css' => '181aa9d9',
@@ -569,7 +569,7 @@ return array(
     'javelin-behavior-differential-comment-jump' => '4fdb476d',
     'javelin-behavior-differential-diff-radios' => 'e1ff79b1',
     'javelin-behavior-differential-dropdown-menus' => '2035b9cb',
-    'javelin-behavior-differential-edit-inline-comments' => '33d4c5e2',
+    'javelin-behavior-differential-edit-inline-comments' => '334267b3',
     'javelin-behavior-differential-feedback-preview' => '6932def3',
     'javelin-behavior-differential-keyboard-navigation' => '2c426492',
     'javelin-behavior-differential-populate' => '8694b1df',
@@ -1027,7 +1027,7 @@ return array(
     '331b1611' => array(
       'javelin-install',
     ),
-    '33d4c5e2' => array(
+    '334267b3' => array(
       'javelin-behavior',
       'javelin-stratcom',
       'javelin-dom',
diff --git a/webroot/rsrc/css/application/differential/changeset-view.css b/webroot/rsrc/css/application/differential/changeset-view.css
index 4cdf7e09ea..5c3c33e5c0 100644
--- a/webroot/rsrc/css/application/differential/changeset-view.css
+++ b/webroot/rsrc/css/application/differential/changeset-view.css
@@ -85,6 +85,10 @@
   user-select:          none;
 }
 
+.differential-diff th.selected {
+  background: {$hovergrey};
+}
+
 .differential-changeset-immutable .differential-diff th {
   cursor: auto;
 }
diff --git a/webroot/rsrc/js/application/differential/behavior-edit-inline-comments.js b/webroot/rsrc/js/application/differential/behavior-edit-inline-comments.js
index 9a3a783a61..101f9ab990 100644
--- a/webroot/rsrc/js/application/differential/behavior-edit-inline-comments.js
+++ b/webroot/rsrc/js/application/differential/behavior-edit-inline-comments.js
@@ -12,6 +12,7 @@ JX.behavior('differential-edit-inline-comments', function(config) {
 
   var selecting = false;
   var reticle = JX.$N('div', {className: 'differential-reticle'});
+  var old_cells = [];
   JX.DOM.hide(reticle);
 
   var origin = null;
@@ -65,10 +66,44 @@ JX.behavior('differential-edit-inline-comments', function(config) {
     dim.setDim(reticle);
 
     JX.DOM.show(reticle);
+
+    // Find all the cells in the same row position between the top and bottom
+    // cell, so we can highlight them.
+    var seq = 0;
+    var row = top.parentNode;
+    for (seq = 0; seq < row.childNodes.length; seq++) {
+      if (row.childNodes[seq] == top) {
+        break;
+      }
+    }
+
+    var cells = [];
+    while (true) {
+      cells.push(row.childNodes[seq]);
+      if (row.childNodes[seq] == bot) {
+        break;
+      }
+      row = row.nextSibling;
+    }
+
+    setSelectedCells(cells);
+  }
+
+  function setSelectedCells(new_cells) {
+    updateSelectedCellsClass(old_cells, false);
+    updateSelectedCellsClass(new_cells, true);
+    old_cells = new_cells;
+  }
+
+  function updateSelectedCellsClass(cells, selected) {
+    for (var ii = 0; ii < cells.length; ii++) {
+      JX.DOM.alterClass(cells[ii], 'selected', selected);
+    }
   }
 
   function hideReticle() {
     JX.DOM.hide(reticle);
+    setSelectedCells([]);
   }
 
   JX.DifferentialInlineCommentEditor.listen('done', function() {
@@ -128,20 +163,59 @@ JX.behavior('differential-edit-inline-comments', function(config) {
     });
 
   JX.Stratcom.listen(
-    'mouseover',
+    ['mouseover', 'mouseout'],
     ['differential-changeset', 'tag:th'],
     function(e) {
-      if (!selecting ||
-          editor ||
-          (getRowNumber(e.getTarget()) === undefined) ||
-          (isOnRight(e.getTarget()) != isOnRight(origin)) ||
-          (e.getNode('differential-changeset') !== root)) {
+      if (editor) {
+        // Don't update the reticle if we're editing a comment, since this
+        // would be distracting and we want to keep the lines corresponding
+        // to the comment highlighted during the edit.
         return;
       }
 
-      target = e.getTarget();
+      if (getRowNumber(e.getTarget()) === undefined) {
+        // Don't update the reticle if this "<th />" doesn't correspond to a
+        // line number. For instance, this may be a dead line number, like the
+        // empty line numbers on the left hand side of a newly added file.
+        return;
+      }
 
-      updateReticle();
+      if (selecting) {
+        if (isOnRight(e.getTarget()) != isOnRight(origin)) {
+          // Don't update the reticle if we're selecting a line range and the
+          // "<th />" under the cursor is on the wrong side of the file. You
+          // can only leave inline comments on the left or right side of a
+          // file, not across lines on both sides.
+          return;
+        }
+
+        if (e.getNode('differential-changeset') !== root) {
+          // Don't update the reticle if we're selecting a line range and
+          // the "<th />" under the cursor corresponds to a different file.
+          // You can only leave inline comments on lines in a single file,
+          // not across multiple files.
+          return;
+        }
+      }
+
+      if (e.getType() == 'mouseout') {
+        if (selecting) {
+          // Don't hide the reticle if we're selecting, since we want to
+          // keep showing the line range that will be used if the mouse is
+          // released.
+          return;
+        }
+        hideReticle();
+      } else {
+        target = e.getTarget();
+        if (!selecting) {
+          // If we're just hovering the mouse and not selecting a line range,
+          // set the origin to the current row so we highlight it.
+          origin = target;
+        }
+
+        updateReticle();
+      }
     });
 
   JX.Stratcom.listen(