Thread:Project:Support desk/spam users/reply

We generally don't recommend deleting users, we instead recomend people either just ignore them, and use the extension:Renameuser extension if they have an offensive, or use RevisionDelete to "suppress" them (Give yourself the hideuser right, then when indef blocking a user, you have an option to hide them from lists. A "suppressed" user is only visible to admins).

Some people use Extension:User_Merge_and_Delete to delete users. I've never used that extension personally, so don't really know how good it is.