The Friends screen in the server settings should allow nicknames for the users (I don’t remember them by their usernames or email addresses)
If you use PlexPy, the add on that allows you to track historical information on your media and friend’s usage, you can do this. Within Plex itself, though, you are stuck with the names they use via their plex.tv log in…
PlexWatch uses friendly names, too. But I think it needs to be edited in the config files. Not sure if the web front end allows you to configure it there or not. I haven’t messed with PlexWatch in a long time now.
