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..8517bef589 100644
--- a/lib/private/Comments/Comment.php
+++ b/lib/private/Comments/Comment.php
@@ -233,6 +233,9 @@ class Comment implements IComment {
 			return [];
 		}
 		$uids = array_unique($mentions[0]);
+		usort($uids, static function ($uid1, $uid2) {
+			return mb_strlen($uid2) <=> mb_strlen($uid1);
+		});
 		$result = [];
 		foreach ($uids as $uid) {
 			$cleanUid = trim(substr($uid, 1), '"');
diff --git a/tests/lib/Comments/CommentTest.php b/tests/lib/Comments/CommentTest.php
index 245ca9693e..7b3254ac14 100644
--- a/tests/lib/Comments/CommentTest.php
+++ b/tests/lib/Comments/CommentTest.php
@@ -51,7 +51,7 @@ class CommentTest extends TestCase {
 		$this->assertSame($object['id'], $comment->getObjectId());
 	}
 
-	
+
 	public function testSetIdIllegalInput() {
 		$this->expectException(\OCP\Comments\IllegalIDChangeException::class);
 
@@ -120,7 +120,7 @@ class CommentTest extends TestCase {
 		$comment->$setter($type, $id);
 	}
 
-	
+
 	public function testSetUberlongMessage() {
 		$this->expectException(\OCP\Comments\MessageTooLongException::class);
 
@@ -149,7 +149,7 @@ class CommentTest extends TestCase {
 					' cc @23452-4333-54353-2342 @yolo!' .
 					' however the most important thing to know is that www.croissant.com/@oil is not valid' .
 					' and won\'t match anything at all',
-				['foobar', 'barfoo', 'foo@bar.com', 'bar@foo.org@foobar.io', '23452-4333-54353-2342', 'yolo']
+				['bar@foo.org@foobar.io', '23452-4333-54353-2342', 'foo@bar.com', 'foobar', 'barfoo', 'yolo']
 			],
 			[
 				'@@chef is also a valid mention, no matter how strange it looks', ['@chef']