i think when people say they recognise users by their signature, they don't always mean the recognise them every where they go and don't have to check the username (though perhaps in some situations that may be the case), but in fact they mean when they are having a conversation, or reading one, it's easier to see the back and forwards by the signature, and then when they've done reading that conversation they'll likely forget who that sig is for.
i remember MRK by his sig and that's about it, but then i've had a man crush on MRK since i can remember