A user (@MaxBioHazard) has reported that he has received mention notification which he shouldn't have, following the notification rule "the message cannot contain any other signatures".
It happened after this test edit and is screenshoted here:
This makes me worry, knowing that when I edit big discussion for testing purposes in my sandbox, users which participated in them may receive notifications.
It is also interesting that both sections named "Комментарии" which, according to the screenshot, must contain link to MaxBioHazard's page, contain no such.