A lot of sites that have a log-in function also have a prominent message on every page saying either "You are logged in as [username]" or "You are not logged in."

Advice to Max: If you're serious about having a policy that people should not be "unnamed" then you should make it impossible to post without putting something in the "from" box. It's silly to have Joe go around nagging people to do this when you could easily force them to do it.