Exactly, they aren't good at creating new material. But many discussions in comment section are simply regurgitations of existing material, which they are good at rearranging. New novel discussions in places like this are actually a very rare thing, as many comment sections are simply people who already know informing those who don't. I'm doing that right now, funnily enough.

Neither are most humans

This is rather moving the goalposts from "plausibly human comment" to "meaningful literature", I think