There's currently no way for account administrators to know whether a user has been active on sites requiring a MusicBrainz login (CB, AB, LB, AcoustID, MeB.org, etc.). Exposing who/what they've authorised (as per a user's /account/applications) would at least give an idea whether they've been active elsewhere.

I'm not sure how or where to expose this, but it would be great if it was possible to see this on at least /admin/user/delete, but possibly also /admin/user/edit - and perhaps a new /admin/user/details?

With the Discourse SSO (MBS-8839), Discourse is no longer OAuth'd, so we may want to look into being able to fetch Discourse information some other way.