well
A) we have no groups just the ranks as mentioned above...although some people like to put ODST or leathernecks in their sig or something
B ) like is not spelled with a "y"
It's alright, I can see why you were wondering. If you mean things such as Sean's "ONI Officer" rank, that's because he's a moderator, and part of the staff.
Some actually get special name or group designation based on what they have done. For example, the people behind Legendary Armor have their own special group name and yet some of them only got less than 20 posts. Check their threads and you'll see why.
yeah, i have a rank, even though i made it up (5up3r 1337), it is pretty relevant of what i contribute, which is, at the moment, knowledge about pepakura, because, uh, check my progress thread.
trust me, its just for laughs, its not necessary, those with them do it because they can, and want the world to know it