It seems like there is some desire to see an automatic functionality, perhaps one that you could turn on and off.

The difficulty is that although it is not too difficult to discern what commenters you appreciate, it is not as easy to distinguish the ones you are neutral towards, and those that you don't care for. At some point it is helpful to know what commenters you do not appreciate. However, only identifying the ones that you do would still likely be an improvement.

I also agree with kleinbl00 on that point. This might reveal other possibilities. doesntgolf makes the point that you might eventually have to rate too many commenters to make this worthwhile. However, it is possible that we could turn this into a functionality that combined the signals of multiple users. For example, if you and I rate a commenters similarly, part of your bias could be used for my sort. Still, I am not sure if that would be a good thing. It does however, create a signal that we don't currently have.

I do think that it might be easy to under appreciate the feeling of being able to do something to improve your comment sort. I'm not sure if it would be the case, but I suspect that it might be an alternate outlet for what might have been a negative comment.