> I find it amusing, but also I wonder what causes the LLM to behave this way.

Forum threads etc. should have writers changing their minds upon feedback which might have this effect, maybe.

Some people are guilty of writing stuff as they go along it as well. You could maybe even say they're more like "thinking out loud", forming the idea and the conclusion as they go along rather than knowing it from the beginning. Then later, when they have some realization, like "thinking out loud isn't entirely accurate, but...", they keep the entire comment as-is rather than continuously iterate on it like a diffusion model would do. So the post becomes like a chronological archive of what the author thought and/or did, rather than just the conclusion.