Yes! I love that idea! As I said to anamirza, I think there's plenty of stuff in the text that indicates he isn't a flat character. JKR isn't always consistent about characterizations--sometimes I feel like character gets subordinated to plot--but I would never say Snape is just randomly mean all the time. This was something I really disagreed with about that premise. He's not cruel to all his students (though he's probably still snarky and cutting). It's specific students he clearly doesn't like personally and he reacts to them in a recognizeable way for him. It's like, in the original thread one poster used the pensieve scene to prove his bastardness because after that moment of sympathy Snape proves he's still a bastard by lashing out at Harry. To me, though, the pensieve just made it more clear why Snape would of course lash out at Harry.

Probably an even better Shakespeare example is Shylock--I mean, what's that about! Howard Bloom has written he was trying to out-Marlowe Marlowe by creating an even worse evil Jew character, but Shylock somehow became the most human, interesting, complex and sympathetic character in the play!