1. Word choice, phrasing, and sentence structure make it seem likely. Ironically, one has to go on vibes. One gets a feel for the voice and tone used by LLMs after a while. It's also a new account with one comment.

2. "Don't post generated comments or AI-edited comments. HN is for conversation between humans." From https://news.ycombinator.com/newsguidelines.html

3. You don't.