Here's a ChatGPT prompt I made and refined with the purpose of generating fake 4chan posts/replies without sounding like an AI chatbot. It knows how to use typical 4chan lingo and sound like a regular poster, and has the ability to understand the context of a thread or an image attached to the post. I plan to make an improved version with more customisability, but this is one I've been using for a few weeks and it gets pretty good results, and never gets called out for being an AI.

https://pastebin.com/dv12EccD

I'll post an example of it in action below.

Enjoy, my /vip/ friends! I will not share this anywhere else.