Reputation for comments?
I have made many useful comments. However, it seems that a useful comment does not reward reputation. Why?
What is the role of useful comments?
In nine out of ten cases, comments should help improving the question or answer at hand.
Once it served it purpose, the comment should get deleted. For example, a request for clarification becomes noise once the question has been edited to fulfill the request.
Reputation simply cannot be combined with the ephemeral nature of comments.