I love this idea—I think it would be fun to gamify it! Keep the predicted thread secret, and then use it to award points to hn commenters based on originality. If a comment is functionally the same as a predicted comment, it gets -10 points. If the comment is novel, it gets 10 points. Then there's a sliding scale between.

You'd need some checks to prevent people from posting a bunch of Zalgo text (maybe a model to identify "interesting" or "insightful" posts), but it could be a fun overlay on the hn commenting ecosystem.