This is reported by many users in ruwiki, though the effect is not as intense as in Iniquity's case for the most.
Also, in my case, "Your alerts" icon becomes red, although no new notifications appear there. Maybe this is connected.
This is caused by T181731: Run maintenance/cleanupUsersWithNoId.php on all wikis. Basically if someone had imported your edits to a wiki, it is now creating your account on those wikis to properly attribute your edits.