It puts every comment into that GPT output detector and colors and writes a short comment on the HN comment, like you see in the screenshot based on a threshold. >0.7 is probably AI, >0.9 is definitely AI. Lower than that is most likely human. Most comments still appear to be human.
It only becomes reliable after about 50 tokens (one token is around 4 characters) so I mark the comments that are too short with gray and make no assessment on those.
I've put it on https://github.com/chryzsh/GPTCommentDetector