Ruwiki admin Wanderer blocked himself, insulting ruwiki community in "explanation" log field [1]. This explanation was hidden [2] by other admin, but it still visible on CentralAuth special page [3] and API query "list=blocks" [4] used by ruwiki script [5] that strikes nicknames of blocked users on talk pages and displays a tooltip with block parameters on hover on that nickname.
Hiding an action comment should hide it from CentralAuth and API too.[1]: https://ru.wikipedia.org/wiki/Special:Contributions/Wanderer777
[2]: https://ru.wikipedia.org/wiki/Special:Log?type=delete&user=&page=&wpdate=&tagfilter=&subtype=event
[3]: https://ru.wikipedia.org/wiki/Special:CentralAuth/Wanderer777
[4]: https://ru.wikipedia.org/w/api.php?action=query&format=xml&list=blocks&bkusers=Wanderer777&bkprop=user%7Ctimestamp%7Cexpiry%7Creason%7Cflags%7Cby
[5]: https://ru.wikipedia.org/wiki/MediaWiki:Gadget-markblocked.js