I saw the "Does upvoting a comment add to the commenter's reputation" question already, but seriously: this seems like a bug, not a feature.
There are questions to which there is no answer, but there is a comment. When that comment is of seriously informational value (either to readers or to the OP) and many upvotes are given, that should result in increased reputation. I could understand it being a lower amount of reputation (similar to an edit? +2 instead of +10?) but it seems like it encourages value-free "answers" to give rep for answers but none at all for comments.