great new spotify feature: when someone sends you a link to a song, it includes a tracking parameter that associates the two of you. when you open the link, instead of going to the song, it goes to your "spotify messages inbox" where you can see your past "conversation" with the person (i.e. every time they've sent you a link with that tracking ID), but does not actually play the song. to play the song, you need to open it from the messaging inbox. when you try to do that, you are invited to join spotify messages. you can dismiss the dialogue, but then the song won't play. you have to join spotify messages to open the song.
