User:MergeDeletion
This is where user accounts get merged into if they ever become uneeded and/or don't follow the username rules.
Because editing the database for users can be risky, Special:UserMerge serves as a safer option. Special:Log/usermerge keeps track of these.
⚠️ Warning: Merging users is permanent and irreversible! So, please double check the username of the account you're going to delete.