As of now you can go to an artist page, press "Relate to...", search for that same artist and try to relate them. It takes you to a Internal Server Error page like this:

http://test.musicbrainz.org/edit/relationship/create?type0=artist&type1=artist&entity0=83f36ab9-beff-4c53-9d34-eee03fcf8672&entity1=83f36ab9-beff-4c53-9d34-eee03fcf8672

The entity from where the relationship is being added shouldn't appear on that list at all.