In ch.11, we have the big Pride vs. Vanity discussion between Elizabeth and Darcy, but what I noticed this time around were the clues leading up to it.
Others have mentioned Mary's sermonette on the same subject in ch.5. What a great way for JA to clarify the difference between pride and vanity (or what *she* considered the difference between them) without sounding pedantic herself, and while giving her readers a chuckle at the same time! I'm sure that most other writers of her time would have put this description in the narration, or in some "serious" character's mouth, to make sure that their readers took it seriously. By the time we get to ch.11, most (non-obsessive) readers would forget *who* had said it and simply remember the difference between pride and vanity!
Another thing I noticed is that in ch.10, Darcy talks rather cynically about humility, calling it "sometimes an indirect boast". I get the impression that he thinks it's at least more honest to be openly proud, and that he is not only proud himself, but by his own description secretly considers pride a kind of virtue, not a defect.
I was just reminded, also, that other languages have two different words for good and bad pride, while English does not. In French, for example, the word for "good" or justified pride is "fierté", while the word for "bad" or unjustified pride is "orgueil". It seems fairly obvious by now that Darcy has both good and bad pride.
On the subject of vanity, it seems that Darcy (like Elizabeth) is vain about his judgement, which is why he is "mortified" to admit that he has changed his mind about Elizabeth!