Index: core/mention_api.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- core/mention_api.php	(date 1555667913000)
+++ core/mention_api.php	(date 1555668521000)
@@ -73,8 +73,8 @@
 			# Negative lookbehind  to ensure we don't match multiple tags
 			. '(?<!' . $t_quoted_tag . ')' . $t_quoted_tag
 			. ')'
-			# any word char, dash or period, must end with word char
-			. '([\w\-.]*[\w])'
+			# any word char, dash, period or single @ char, must end with word char
+			. '([\w\-.]*@?[\w\-.]*[\w])'
 			# Lookforward to ensure next char is not a valid mention char or
 			# the end of the string, or the mention tag
 			. '(?=[^\w@]|$)'