I'm also one of the people who would prefer to use a regular name on a GM. I guess have the prefix in front of your name makes it seem a little more professional, but in all honesty, the regular name just seems more natural to me.
Plus, it's easy to tell a GM from a regular player by A) Either paying attention to the guild name/title. B) If they're using a GM sprite (obviously) and the name is yellow, and if a scammer tries to come along, no GM will (or shouldn't) ask for account information.