I would like to suggest a rating system, based either on a 1-10 scale or whatever.
This rating system would be allowed for everyone, with or with an account.
I see that this can have a negative impact on the artist where they cant know why they got a bad/good rating(making it not true feedback), but often, a comment is a lot of effort for a casual listener, and they'd rather just leave a quick unexplained rating.
I believe a rating system would allow for a quick feedback system with little effort on the listeners part, and a quick way to give feedback.
Myself, I am actually quite in a battle with myself if its a good idea or not, and its rather unlikely you, the dev. haven't thought of it, but for the most part where I can agree with myself, I think it would be a good idea.