What's messy and what's not? Real usernames conflicts seem pretty rare nowadays and it's not really a problem in general, nor you can predict when it will.[1] Really messy situations might be when a user has more edits and would get the global account but another one is sysop somewhere else, or when unattached accounts are active in multilingual wikis. Anyway it could be useful to know (and not hard to query) how many user accounts are there 1) with some activity in the last year, 2) not fully unified on all CentralAuth wikis, 3) nor fully unifiable by email or password. 3) is very important: there are still many unique usernames whose owner didn't care to unify yet and perhaps we should suggest them en masse to merge accounts. Nemo [1] For instance, there are dozens of "Nemo" who happily live alone in their pet projects because I didn't try to usurp them.