It wouldn't be an HN comment thread without a 100% confident, no-room-for-doubt assertion of AI-generated writing.
Plenty of comment threads don't have anybody saying that the original article is AI. It tends to be for articles that aren't AI-generated.
HN has a lot of people submitting/upvoting AI-generated content, and also a lot of people who work with AI extensively and therefore know how to identify it. It's not a big surprise.