Along with when they joined and what house they're in, you could see when this user has last logged in to the site. This would only be visible when you see them under the "all users" option. There are some welcoming teams on NL that check when a person has last been online, and it would be soooo much easier if it were visible on the Marauder's Map. It's also easy to check when your friend was last online!
Customer support service by UserEcho