diff -u b/core/modules/comment/comment.tokens.inc b/core/modules/comment/comment.tokens.inc
--- b/core/modules/comment/comment.tokens.inc
+++ b/core/modules/comment/comment.tokens.inc
@@ -148,9 +148,7 @@
           break;
 
         case 'mail':
-          // Check identicality, because getOwnerId() returns NULL if there is
-          // no ID, which evaluates to 0.
-          if ($comment->getOwnerId() !== 0) {
+          if ($comment->getOwnerId()) {
             $mail = $comment->getOwner()->getEmail();
           }
           else {