And they'll get banned by moderators. Ultimately that's the key ingredient in any good strategy here: human curation.
AI bots will get the confidence of admins and moderators. They will be so helpful and wise that they will become admin and moderators. Then, they will ban the accounts of the human moderators.
Mods will ban them and new users will be forced to verify via voice/video chat/livestream.
We already have AI generated audio and video. This is a stopgap at best.
Maybe the mods will have to trick the AI by asking it to threaten them or any other kind of “ethical” trap but that will just mean the AI owners abandon ethical controls