The interface messages mentioned in the title both say "Cannot create account: The requested username would conflict with another username on another wiki.". For new users (who are the people who will see this), this can be a bit cryptic, so I propose changing the wording to "Cannot create account: The username is already in use. Please pick another name."
Related Gerrit Patches:
|mediawiki/extensions/CentralAuth : master||"account exists" messages reworded|
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|Open||None||T40638 Interface messages needing rewording or documentation and other issues with existing messages (tracking)|
|Resolved||Sumit||T90732 The messages Centralauth-account-unattached-exists and Centralauth-account-rename-exists should tell the user what to do|
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