It's probably hard for me to relate with your problem, because I'm literally never interested in most recents comments. What is your "usecase" in reading newest comments?
I mean, the same reason why you'd want the newest of anything. Stuff on the top gets out of date. Even in the context of a comment thread, I'd want the latest comment in the thread, etc.
Not to mention with threads you waste time reading things over and over again.
Not to mention with threads you waste time reading things over and over again.