This is something that works better on paper in practice. Namely, there are a hell of a lot of false positives of AI use which frequently causes shitstorms on social media where someone says "AI?" in bad faith and now the OP has to defend themselves and in the case of writing a blog post there aren't as concrete ways to defend yourself. (no, demanding the edit history of the post is not reasonable)

Hacker News adopting such a feature would likely do more harm than good.