Even before the Philosopher's Stone eleventh hour plot twist revealed that Quirrell was actually a baddie with a Voldemort-shaped tumor growing out of his skull, the ill-fated Defense Against the Dark Arts professor was never topping most people's favorite character lists. As a regular guy, he's whiny and twitchy to the point of cartoonishness, and as a villain, he's weak-willed and naive. One has to assume that a large part of this is down to his parents being awful people and naming him Quirinus. But regardless, people weren't exactly weeping over his death. That said, you can't help but feel a little bad for the pathetic creature who was left all alone to die. And with Quirrell being the first real death of the series, it certainly carries a bit of shock value, both in Voldemort's callousness and the almost casual way that Dumbledore informs Harry about it.