If I'm reading things right here, then the following is my viewpoint.
All jokes aside, there is nothing in game that can be related to Hell, as it is thought of in real life. Therefore, a guild by the name Hells Dwarves is not within the setting of the game, therefore ooc, therefore not appropriate for use in game, therefore should be immediately changed.
With what has been made and revealed of the game's settings, there is no concept of hell. Therefore using that word as it is being used is completely OOC, and since the game is trying to limit the ooc stuff in game, it should not be used in game.
And not to bring up that topic again, but if people made a fuss over the word bugger, then I will imagine that they will be voicing quite a conern over the allowing of the word hell in game.