Scott uses WP, and it has plenty of comment ranking plugins. Here is one popular blog with a simple open voting system: http://www.preposterousuniverse.com/blog . It is probably not good enough for SSC, but many other versions are available. As I said, Scott is not interested in improving the commenting system, and probably is not interested in taking any steps beyond great writing toward improving the blog's popularity, either.
Here is one popular blog with a simple open voting system: http://www.preposterousuniverse.com/blog
That has voting but it doesn't seem to have threaded comments. That means switching to that plugin would break all the existing comment threads.
As I said, Scott is not interested in improving the commenting system,
I would guess that the main issue is that he doesn't want to do work to improve it.
Arguing what's an improvement also isn't easy.
If I look at the blogs of influential people who do put effort into it, I don't see that they all use a comment solution that Scott refuses to use.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.