I find it interesting that Darcy, from whom you have come to expect reserve and circumspection, does speak the unveiled truth on occasion. Does it not tend to be, when he can’t keep from teaching Miss Bingley a lesson? She can certainly be annoying.

As in
C:I can guess the subject of your reverie…
D:My mind more agreeably engaged … his admiration for Miss Bennet’s fine eyes.
C:I fear this has lessened your admiration for her fine eyes?
D:Not at all, they were brightened by the exercise.
C:Will she be as tall as I am?
D:She is now about Miss Elizabeth Bennet’s height …
C:Yada yada on acomplishments while Lizzy has been reading
D:She must add something more substantial….improvement of her mind by extensive reading!
And of course the famous whatever has affinity to cunning is despicable!
Miss Bingley is playing and singing – at Darcy’s request - and what does he do, if not ask Elizabeth about her inclination to dance!
Caroline attempts to tease him mentioning his having a portrait of Elizabeth in the Pemberley gallery and rather than being provoked he plays along, mentioning the expression of Lizzy’s eyes and their remarkably fine eye-lashes!
And of course, the turn about the room that backfired. No wonder Miss Bingley fled to the pianoforte.