It might be something they can fix. All of 1.0 my friend couldn't use his preferred name because it had the letters "GM" in it, with GM being a prohibited name for obvious reasons. Apparently it didn't even matter if it was in the same word, so not only would something like "magma" be unusable, "Bog Man" was potentially unusable. Turned out it was a bug and he can use his name now. Maybe it is something similar.