"It's interesting hearing about the culture of mailing lists not using usernames"

Well, there were some people who did. If you ever encounter a username that starts "Knight-" or goes "Cousin ----", there's a fair chance it belongs to an old Forever Knight fan.

However, a lot of people used their own name. Also, there were others who used an pen name that looked just like a regular name. Maybe their close friends knew it was a pseud, but most people didn't.