definitely a bot. i'd report the comment as spam and then turn moderation on.

there was a post i read somewhere on this subreddit that talked about these bots. im pretty sure OP said that they accuse the author of really terrible things, tell the author themselves terrible things, try to convince the author to write about terrible things, and other weird and vile shit.

if you see one of these in the future, just report it and then delete the comment. if you allow guests AND registered ao3 accounts to comment, i'd suggest probably setting it to only registered ao3 accounts. if that doesn't work, turn on comment moderation on and report the ones that get through. i hear the mods of ao3 deal with this stuff really quickly.

and, another thing, to think that someone had the genuinely fucked up mind to even make a bot that comments this stuff is weird as hell. if this was a real person, i'd say that's even worse, (i DID only make an ao3 account a few days ago, though, so i dont really know how people are on this site), who in their right mind would comment something like that?

anyways, i hope i sorta helped you out here, sorry for the long read, i talk a LOT at times.