Index: src/applications/differential/mail/DifferentialCommentMail.php
===================================================================
--- src/applications/differential/mail/DifferentialCommentMail.php
+++ src/applications/differential/mail/DifferentialCommentMail.php
@@ -56,7 +56,10 @@
         break;
     }
 
-    if (strlen(trim($comment->getContent()))) {
+    $has_comment = strlen(trim($comment->getContent()));
+    $has_inlines = (bool)$this->getInlineComments();
+
+    if ($has_comment || $has_inlines) {
       switch ($action) {
         case DifferentialAction::ACTION_CLOSE:
           // Commit comments are auto-generated and not especially interesting,
@@ -68,6 +71,10 @@
       }
     }
 
+    if (!$tags) {
+      $tags[] = MetaMTANotificationType::TYPE_DIFFERENTIAL_OTHER;
+    }
+
     return $tags;
   }