What struck me about this passage was the sheer subtlety of the clues Anne had to work with to discover CW's love. Of course, we readers are inclined to believe that Anne is right and that CW *does* love her ;-), but what if she hadn't been paying attention, or hadn't been able to read CW's code?

[CW's] choice of subjects, his expressions, and still more his manner and look, had been such as she could see in only one light. His opinion of Louisa Musgrove's inferiority, an opinion which he had seemed solicitous to give, his wonder at Captain Benwick, his feelings as to a first, strong attachment; sentences begun which he could not finish, his half-averted eyes, and more than half-expressive glance.