Isn't the Fire Discord a public server, one that anyone can request to join? That doesn't really make your Discord username "private" anymore if it's that easily accessible, not to mention that it'd be a server with a large number of people in it.

(note: I'm aware that it's probably Fire Flight members only, however, I do faintly recall a friend saying to me a while back that someone in that server can invite one OOF person, but please correct me if I'm wrong. I'm not in Fire.)