A lot of MMOs won't let you name yourself after a government or military title. Because ... new players might think that makes you a GM or something? I dunno.

I do know they've got a banned-name list, and also (like you found with 'Duchiss') that it doesn't adjust for even minor misspellings. Which would explain why I (briefly) saw a Roe named Adolf Hilter running around. With the mustache and army uniform and everything