I think it would be great if you could comment on songs that people have sent you, so you can say, liked this, didn't like this etc. At the moment I tend to send the same song back with a comment saying what I thought of it, which is a bit messy.
Spotify does not work. There is no help out there. No solutions. Make Spotify go away.
wearehunted.com do this really well. Each song has a little icon next to it if someone has commented on it, and you can easily see their comments. It would make Spotify way more social - if you see an intelligent or like-minded comment you could follow that user.