Harry always half-expects to be told to be quiet when he starts talking (which is probably why he talks so loudly, and tries to get everything out all at once). Enjolras's habit of not only letting him go on, but waiting expectantly for him to do so still takes him by surprise.

"But I think I cannot answer truly until 'tis put to the test. Rollo's fight I could not deny-- perchance other causes will seem so plain."