Hermione's reply, along with the way she wriggled her backside, certainly made him grin. Uncomfortable or not, she still seemed to be enjoying herself. Of course, hearing her call him 'sir' in this context felt a bit wrong, but at the same time, it was thrilling. In light of that, there really was no way he could have kept from moving. On the other hand, he still didn't rut away how his hips told him to. Instead, he moved slowly and gently, fingertips ghosting over her skin, in spite of how loudly that tiny bit of movement made him groan.
"God, you feel good," he whispered, eyes rolling, before he groaned again. But he wasn't going to speed up. Not unless she asked him to. Though there wasn't anything wrong with hoping she'd ask him to, was there?