Is it possible to generate a list of all the active editors, at all the wikis, that have the same error?
I've settled on sending error-specific messages, and I've written one at m:User:Whatamidoing (WMF)/Custom signature that is being translated. If we can make a list in MassMessage format later this month, then one of my teammates will use Tech/News' magic multilingual script to send the translated messages to everyone.
Could you generate that list (for just the one error – I'm starting with mismatched usernames), or do we need to go through each wiki separately and add them all up?