The only way to remove the changeset comment is to redact the edit. I'm happy to do that if that is what you request.

to change your user name, go to My Profile, upper right, select My Account there you can change your display name. I will say, a lot of people use their real name but if you want more protection, then that isn't a bad idea. Your original user name will exist forever but only your current user name will show on your future edits.