I may have misstated my case. I agree about how he went into the room at Hunsford and by his own admission he wished to think better of his own worth than those outside his circle. He is “properly humbled” by Lizzy’s response. In that way he has changed significantly. But, I also think the very fact that he took her reproofs to heart and worked to improve himself rather than simply resenting her for it says a lot about his character.
My real point was that while all this is true, what Mrs. Reynolds says of him is
also true (and Wickham says some of the same things though he makes excuses for it) and has been true all along.
We do see that Darcy can behave in a gentlemanly manner. But after the proposal he seeks out an introduction to the Gardiners and toward the end he behaves with civility toward Mrs. Philips, Sir William and Mr. Collins. This is what I mean by his manners have improved. He was always capable of good manners but now he is making more of a point of behaving well and toward a broader range of people.