Don't get me wrong, I have come to appreciate that the whole reputation concept that stackoverflow employs is a highly evolved process. It is awesome! It effectively separates the useful information from the just plain wrong information. No doubt, this is what makes the whole concept work extremely well.
Why shouldn't the same criterion apply to comments?
It doesn't seem symmetric to me that comments allow only for up votes (with no reflection to the comment-er) and at the same time disallow the down voting of useless comments (which in a perfect world would be somehow reflected).
Comments are usually read along with proposed answers. When someone posts anything, it only seems right for their text to be fairly judged by the existing community-of-trust. This is why stackoverflow works so well.
Some comments are useless; some comments help in clarifying the proposed answer. This distinction is a relevant factor for judging someone who participates in such a forum. Why the asymmetry?
I have tried to think of reasons to the contrary, and all I ever come up with is "They just asked for clarification, why should they be punished?" In the real world, I don't think any comment asking for useful clarification would be down-voted, at least not for long.
I don't know what the metrics should be, but ignoring this information just seems wrong.
In my mind, we are all contributing something. The faster we can separate the useful from the useless, the more effective this paradigm becomes. What am I missing?