4chan style makes it easier to see which comments are new. However it does so at the cost of separation of subtopics. IMO 4chan style is not a good fit for HN because we often have many different conversations going on at the same time within the discussion of a story. If HN switched to 4chan style comments I believe that it would dramatically change the nature of the discourse for the worse.

I wouldn't like 0 threading, but I strongly dislike the depth of threading on HN for some reason, I find it hard to follow as it gets progressively narrower.

The 4chan post referencing (>>>/g/565645674567/) which allows you to reference any post from any board and it embeds itself on hover is a very underused useful feature I believe.