I believe I've seen some comments that may have been LLM-generated. Typically they're top-level, short (1-3 sentences), somewhat on topic, but barely relevant to the conversations happening.

Like, for example, on a post of a blog post about a malicious package found in NPM is I'll sometimes see a post like; "NPM is a godsend for developers. Problems can occur, but it has helped developers move more quickly and has made sharing code a breeze."

I never report it since I'm not quite sure if it's generated by a program, or merely just a low-effort comment from a human. Which is tricky.