That's nothing. Someone trained a GPT-J 6B model on 4chan and then let the model loose on the forums for a day. It took about 15k messages until people suspected something was off, and even that was because the country flags, Seychelles, a rare flag on 4chan, were a giveaway.

video: https://www.youtube.com/watch?v=efPrtcLdcdM

model: https://huggingface.co/ykilcher/gpt-4chan