I agree that having names of any Chapter such as Ultramarines, Imperial Fist etc for a specific group of people to use is a bad idea, I think we as a community at this stage are the tip of the iceberg, once the game gets more attention you're going to serious damage not only to the lore side of the game but social side as well.
So I could be Ultramarine, from Ultramarines clan that is part of Ultramarines chapter. That's just fucked up. Edit: I stand strongly with Tornadium in this debate. Editedit: And everyone who are going to copypaste their guild name straight from the lore shame on you!
You don't HAVE to satisfy everyone. It's going to piss a lot of the core warhammer fans off. Those are the hardcore community that keep your game running.
Then why'd you "flip my shit" if somebody took the name of 'Ultramarines Clan'? As Kanthric said there are some reasons to why exact names should be taken, but the rest really should be first come, first serve. If somebody wanna name their shitty clan 'The Real Ultramarines' or something corny as that then I'm pretty sure they'll be the ones that are sorry in the end.
Oh you can be a Dark Angel, from Ultramarines clan that is part of Ultramarines chapter. That's really fucked up!
Not to forget to be an Eldar from Sons of Horus clan that is part of Biel-Tan...how fucked up is that?