Snape stared at Al. He'd never heard anything quite like that in his life. This was an extremely intelligent - and judging by his outbursts, really quite powerful - wizard. Who had to practice drinking. Who had to memorise a firstie's charm, through repetition.
Clearly, those outbursts, the emotional repression that prompted them, were the tip of a whole mental iceberg of pure crystallised Weirdness.
Lesser Legilimenses than Snape would have been utterly intrigued.
"I'd like you to try again," he replied with equal calmness.
"This time, I want to watch closely, so I can see what goes wrong. To watch closely enough," he added, "I'll need to be inside your mind as you cast."