Can't you set it so that if you agree with an answer, you can rate it, but maybe in a different colour. PLEASE. Then if someone doesn't reply or rate, others can.... PLEASE
This IS a good idea. Users should be able to rate each other's answers as to how useful they are, like in book ratings for Amazon. The ratings system as it stands really doesn't work anyway. I rarely have time to rate, and when I do I always give everyone 3 stars as I think it's mean not to!!