I doubt there are any communities that deal specifically with writing for games-- which I have had to do a few times. It could be kind of interesting. It would be nice to establish basic game writing concepts. Emphasizing brevity and clarity for example.
Crazyfinger is right in that its less about professional critique, and more about finding some entertainment within an active and varied community. [Almost] everyone likes a good story, and [almost] everyone has tried to write one; why not allow people with similar interests and skills to share that? For example, I've done…