Musicbrainz has collections, it would be a good idea to integrate synchronizing between listenbrainz and musicbrainz.

When you srobble a track (containing mbid's) you should have a feature that will then write this back to a musicbrainz collection.
As there are now more types of collection it should be possible to write to an artist and a recording collection.
ie the user could create a collection "Artists that I have listened to" and "Recordings that I have listened to"
There needs to be the ability to nominate a specific collection from the list that the user has.