They're a widespread issue.

I personally hate the marketboard bots. Every five minutes they undercut by one whole gil. Always a retainer from Limsa with some gibberish name. Unfortunately they aren't stupid enough to undercut down to 1 gil, else I'd be taking advantage of them all night long.

The more predatory ones are in Endwalker fate zones. Presumably using stolen accounts to farm fates, in shell FC's. Reported them a bunch of times, nothing seems to be done, they've evaded plenty of ban waves.