It has been requested a couple of times now and we looked into doing it at one point too, but it would be nice to provide links to a number of the *Brainz sites directly from the forum site.

See e.g., https://community.metabrainz.org/t/link-between-community-and-musicbrainz/183?u=freso (maybe?) and https://community.metabrainz.org/t/clickable-link-on-these-forum-pages-to-musicbrainz/335088?u=freso.