] Second, I don't understand the exchange between the two of them after Lizzy and Caro take a refreshing turn about the room at Netherfield. Lizzy tells Darcy that "Your defect is a propensity to hate everybody." Seems an ungenerous speech on Lizzy's part when she had been jauntily sparring with him just moments before. What's that all about?

I think Lizzy was using Mr Darcys confession that he never forgave anybody he felt had made an offence to him. So first she calls it "implacable resentment", which I think is more unyielding than Mr Darcys own description. His answer to that is about natural defects to which Lizzy promptly sharpens her answer to "propensity to hate". I think that she thought Mr Darcy was saying that she was too uneducated to understand his meaning and she tried to get the last word by calling him hateful. Mr Darcy gets the last word though but I think he found her mind more challenging than he assumed a young countrybred womans mind to be.