] 3) In chapter 42, the narrator says "Kitty might in time regain her natural degree of sense ..." So Kitty is by nature sensible, and she used to have sense, but lost it? Did anyone else find this to be quite the opposite of what they had thought of Kitty before?

I have always thought of Kitty as a follower, one who is influenced by those closest to her. Because Lydia is so headstrong and Kitty is closest to Lydia in age, she naturally falls into Lydia's orbit at the beginning of the novel. This situation is reinforced by Mrs. Bennet's indulgence of Lydia's whims, and Mr. Bennet's neglect of his younger daughters.

SPOILER: By the end of the novel, Lydia's influence is removed and Kitty falls under different influences (sorry for jumping ahead, but Chapter 61 is most relevant here):