reverted:
--- b/core/modules/contact/src/MailHandler.php
+++ a/core/modules/contact/src/MailHandler.php
@@ -127,16 +127,16 @@
 
     if (!$message->isPersonal()) {
       $this->logger->notice('%sender-name (@sender-from) sent an email regarding %contact_form.', array(
+        '%sender-name' => $sender_cloned->getUsername(),
-        '%sender-name' => $sender_cloned->getDisplayName(),
         '@sender-from' => $sender_cloned->getEmail(),
         '%contact_form' => $contact_form->label(),
       ));
     }
     else {
       $this->logger->notice('%sender-name (@sender-from) sent %recipient-name an email.', array(
+        '%sender-name' => $sender_cloned->getUsername(),
-        '%sender-name' => $sender_cloned->getDisplayName(),
         '@sender-from' => $sender_cloned->getEmail(),
+        '%recipient-name' => $message->getPersonalRecipient()->getUsername(),
-        '%recipient-name' => $message->getPersonalRecipient()->getDisplayName(),
       ));
     }
   }