Usernames are not unique. If you go to Users and search for John, you'll have hundreds of hits. Anyone can name themselves anything they want, as well as rename themselves whenever they want. The system instead uses user IDs as the authoritative reference. For example, you are user 772394, and I am user 208574.
In theory, it becomes possible then for a user to name themselves to the same thing as a moderator. To prevent this. moderators are distinguished by the ♦ by their name.
The real Thomas Ward will have their diamond, and will look something like this on the site:
Otherwise, usernames are almost a free-for-all. Diamonds, as well as some other characters, may not be used in usernames.