Why have both "username" and "display name"? At first I thought it was an extra layer of security , like most online games have, to discourage username/passwor

Why have both "username" and "display name"? At first I thought it was an extra layer of security , like most online games have, to discourage username/password bruteforcing. (It's an obscurity layer, but obscurity layers are not by definition bad.) But you need to tell others your username to communicate with them.