It’s possible that it varies by forum.
I leave a few spammer posts online when they provoke discussion, but most of them get deleted. The quality is very low, and it’s often easy to tell when something is written by AI. If I feel like something I’m reading is AI, I start losing trust in the source. I’m not an AI Luddite, but I don’t want to read AI-generated content unless I know it’s generated by AI.
If I see that someone is using AI in the forum, I immediately put a stop to it because trustworthy content is one of the forum’s most important assets.
Also, what looks passable to humans in 2024 might be easy for people to detect as AI in 2034, kind of like how movie effects that once looked realistic decades ago are now immediately detectable as fake. I think AI-generated content from 2024 is going to look dated eventually.