Heine's had worse looks, so his only response is to raise his eyebrows.

A group of Hufflepuffs had been sent to the infirmary, he remembers that much. They'd been hexed so that their mouths were unusable. Pretty messed up, but the harm had been reversible.

"Well, don't do that." Yes. That's what he's supposed to say. Heine wracks his brain for the rest of the lecture he's supposed to deliver. "It's not safe. Especially if you're doing it to a bunch of people at the same time."