I’ve been looking to implement this since it was first asked, and here it is! Instead of sending me a private message to get your username changed, you can now do so through your profile settings.
Your username can only be changed once every 30 days, and you must have been registered for at least 24 hours.
You’ll also be able to use the “Incognito Mode,” which hides from your fellow Megami Fuse members your previous username. Keep in mind that team members will still be able to see these past usernames, for security reasons.
Follow this link to change your username.