Way back in October 2009 Reddit introduced their "Best" comment sorting system. We've just pulled those changes into Less Wrong. The changes affect only comments, not stories.
It's good. It should significantly improve the visibility of good comments posted later in the life of an article. You (yes you) should adopt it. It's the default for new users.
See http://blog.reddit.com/2009/10/reddits-new-comment-sorting-system.html for the details.
I'm curious whether the math still works correctly on a site where the default karma is 1 instead of 0. But since it's magic to start with, I guess "meh". Let's just not use it to calculate CEV or anything. ;-)