If upvotes on comments were "valuable", I think you'd need to add downvotes on comments and make the downvotes have negative value, because otherwise they'd skew people's rep misleadingly.
And the result would merely be amplification of rep based on whether people had posted comments under their own answers or not. You'd see an explosion of use of the comments system for things that had previously gone into answers, probably making the answers less readable. Then people would want code snippets to work in comments.
I think the votes against comments are not about rep. They're just a quick way for someone else to say "I would have said the same thing" without having to type it out. If someone disagrees, they can write a comment of their own saying why.