I also saw the user (and the corresponding topic) that you're referring to, and I mentioned it as well. Such usernames are misleading, and could even be claimed as imposting actual moderators (or other users in other cases). I understand that only a fool would fall victim from a user named "officialmoderator" with a newbie rank, but still, it would suck for someone ignorant to actually believe he's a moderator of the forum.
Any name containing admin, moderator, including the username of most reputed ones like theymos should be under restrictions for registration.
This is the most correct approach, although some smartasses may still find "alternatives" to this rule, or some might create accounts imposting other users, it still deals with some people automatically, the rest should be reported manually from us, the daily users.