It's because he set his options to not allow others to see what he's doing when he's logged in.Anybody can do it, it doesn't show what you're doing but it still shows you're online, and it italicizes your name.
That takes real dedication, Iban.
I think Tails also has his name italicized when he's on the forums. It may have to do with them being one of the older members of the forums?