I think, at the end of the day, there really isn't much of a difference between the two, for authentication. One is just a public part of who you are, and remai

I think, at the end of the day, there really isn't much of a difference between the two, for authentication. One is just a public part of who you are, and remains fairly static. An argument for keeping the username separate is it is often used for identification. That is, you identify on this site as alberth. Not as any biometric scan. Even if you change which finger you want to use to authenticate, you'd still be alberth to everyone else here. I think there are arguments on favor of letting you change a display name. Probably still would keep a name that is static. (What Twitter does?)