Apparently one of the lemmy.ml admins was overzealous in banning all User-Agent strings that contained the string “bot”. Bans were entered for all of the individual strings containing that word which were observed in their webserver logs, which impacted kbin’s reported agent of “kbinBot”.
The issue has been fixed, and I observed that one of my kbin posts to a lemmy.ml community was successfully pushed to the original instance.
From the response it is likely that many other specifically identified phrases which do contain the word ‘bot’ have indeed been blocked (presumably still are).
The slight variations in kbinBot which were subsequently tried wouldn’t previously have shown up in the logs and so wouldn’t have been added to the blacklist.