The Omniscient Narrator originally described Darcy as "haughty" back in ch.4:

Bingley was by no means deficient, but Darcy was clever. He was at the same time haughty, reserved, and fastidious, and his manners, though well-bred, were not inviting.

I noticed that in chs. 35 and 36, Darcy is twice called "haughty", directly from Elizabeth's POV:

[Darcy] had by that time reached [the gate] also, and, holding out a letter, which [Elizabeth] instinctively took, said, with a look of haughty composure, "I have been walking in the grove some time in the hope of meeting you. Will you do me the honour of reading that letter?"

After reading the letter, Elizabeth's reaction is:

[Darcy] expressed no regret for what he had done which satisfied her; his style was not penitent, but haughty. It was all pride and insolence.

I agree with Cheryl - there is something admirable about the way Elizabeth can get past Darcy's off-putting style to acknowledge that what he writes is probably true.