diff --git a/apps/comments/lib/Activity/Provider.php b/apps/comments/lib/Activity/Provider.php
index 527c9c4ca6..fca3b9e75d 100644
--- a/apps/comments/lib/Activity/Provider.php
+++ b/apps/comments/lib/Activity/Provider.php
@@ -213,17 +213,11 @@ class Provider implements IProvider {
 					continue;
 				}
 
-				$pattern = '/(^|\s)(' . '@' . $mention['id'] . ')(\b)/';
-				if (strpos($mention['id'], ' ') !== false) {
-					$pattern = '/(^|\s)(' . '@"' . $mention['id'] . '"' . ')(\b)?/';
+				$message = str_replace('@"' . $mention['id'] . '"', '{mention' . $mentionCount . '}', $message);
+				if (strpos($mention['id'], ' ') === false && strpos($mention['id'], 'guest/') !== 0) {
+					$message = str_replace('@' . $mention['id'], '{mention' . $mentionCount . '}', $message);
 				}
 
-				$message = preg_replace(
-					$pattern,
-					//'${1}' . $this->regexSafeUser($mention['id'], $displayName) . '${3}',
-					'${1}' . '{mention' . $mentionCount . '}' . '${3}',
-					$message
-				);
 				$mentions['mention' . $mentionCount] = $this->generateUserParameter($mention['id']);
 				$mentionCount++;
 			}
diff --git a/apps/comments/lib/Notification/Notifier.php b/apps/comments/lib/Notification/Notifier.php
index 9f69e5599f..20e0667d14 100644
--- a/apps/comments/lib/Notification/Notifier.php
+++ b/apps/comments/lib/Notification/Notifier.php
@@ -195,7 +195,11 @@ class Notifier implements INotifier {
 			// could contain characters like '@' for user IDs) but a one-based
 			// index of the mentions of that type.
 			$mentionParameterId = 'mention-' . $mention['type'] . $mentionTypeCount[$mention['type']];
-			$message = str_replace('@' . $mention['id'], '{' . $mentionParameterId . '}', $message);
+			$message = str_replace('@"' . $mention['id'] . '"', '{' . $mentionParameterId . '}', $message);
+			if (strpos($mention['id'], ' ') === false && strpos($mention['id'], 'guest/') !== 0) {
+				$message = str_replace('@' . $mention['id'], '{' . $mentionParameterId . '}', $message);
+			}
+
 			try {
 				$displayName = $this->commentsManager->resolveDisplayName($mention['type'], $mention['id']);
 			} catch (\OutOfBoundsException $e) {
diff --git a/lib/private/Comments/Comment.php b/lib/private/Comments/Comment.php
index 7368425174..c838e9571c 100644
--- a/lib/private/Comments/Comment.php
+++ b/lib/private/Comments/Comment.php
@@ -233,6 +233,7 @@ class Comment implements IComment {
 			return [];
 		}
 		$uids = array_unique($mentions[0]);
+		usort($uids, 'mb_strlen');
 		$result = [];
 		foreach ($uids as $uid) {
 			$cleanUid = trim(substr($uid, 1), '"');