It was my impression that this sort of colloquialism/grammar laxity (phrasing questions with straight word order and a question mark/inflection is a modern sort of informality, not a 200 years old one - although it's possible that it only made its way into written English recently. The way I understand it, classical writers tended to keep the elite/normative forms of expression, contrary to modernish writers who tend to mirror everyday speech and slang in their writing. I understand JA used contractions and colloquialisms when put into the mouth of her less refined, less educated, vulgar characters (Lydia, Mrs. Bennet). I recognize, of course, that as a non-native speaker I will not recognize every subtlety and informal usage the way a native speaker does.
