When the character naming was updated to allow the inclusion of spaces, I believe the new naming rules (3 characters before or after a space) has bled into the naming of guilds. For example IX Dread Guard or something that that uses 2 characters before or after a space in the name. I've done several tests with this to make sure that it's not just the name being taken, and I was unable to create any guild with 2 characters before or after a space. I don't believe this was an intended result of the new naming rules and would like to bring this to the attention of the development team.
-Lpolk