He's only silent because he's too thick to string two words together.

“STEALING THE CAR, I WOULDN’T HAVE BEEN SURPRISED IF THEY’D EXPELLED YOU, YOU WA…”

“Voldemort uses people his enemies are close to. He's already used you as bait o…”

“Hello, Harry!” she said.“Er — my name’s Barny,” said Harry, flummoxed.“Oh, have…”

“It's a strange thing,but when you are dreading something and would give anythin…”