It would help if you listed the exact reason given in the e-mail. However, if I were to guess, I would think that the person declining it was thinking of the canon surname Horn, which is disallowed. It's at the discretion of the team member if they think a name is sufficiently close to a canon name as to be attempting to circumvent the rules.
____________"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."
Only fools and children dream of heroes.