"She had seen enough of [Mrs. Ferrars's] pride, her meanness, and her determined prejudice against herself..."
From chapter 8:
"A woman of seven-and-twenty," said Marianne, after pausing a moment, "can never hope to feel or inspire affection again...
Strangled by the Red String: The novel never really explains why Edward and Elinor fell in love, focusing much more on Marianne's romantic relationships. Emma Thompson went out of her way to rectify this in the film, to the point where many fans consider the film superior, at least in this regard; the 2008 miniseries takes its cue from Thompson's screenplay, and is much the better for it.
Edward's persisting in the engagement is portrayed as the honorable thing to do. However, the modern reader can't help noticing that Edward's stance would lead him to a life-bonding contract with an individual he no longer cared about. The engagement is also technically void (made by two minors without their parents' consent), meaning it's not legally binding; Edward sticks to it because he feels morally bound. As one fanfiction writer puts it, "I made a promise when I was a teenager, and it is only honourable that I be bound by this promise for all eternity." With that said, Edward's breaking off the engagement after its reveal would have ruined Lucy's reputation and destroyed her chance of ever marrying, let alone marrying well. Given her financial situation, that would be a sentence to ruin. Only women in the Regency era could break off an engagement, and even then it was a risk; Lucy only got away with it because she married Robert immediately thereafter.
Girls are considered able to marry much younger than in modern times. When sixteen-year-old Marianne objects that Colonel Brandon (35) is old enough to be her father, this is treated as a sign of her immaturity and Mrs. Jennings says that it's better to marry an older man whose character and position in the world are fixed. (There's also the fact that Brandon is attracted to her because she resembles his teenage ward who resembles her mother, his Lost Lenore.) Willoughby's crime of impregnating and abandoning Eliza condemns him, but not the fact that she's even younger than Marianne.
Wangst: Deliberate — Marianne's response to her romantic woes begins to take on this edge, which to her credit she eventually comes to realize.
Crowning Moment of Awesome: Emma Thompson's Best Adapted Screenplay win makes her the only person to have won Academy Awards for both writing and acting. (She got Best Actress for Howard's End.)
Crowning Music of Awesome: Patrick Doyle's soundtrack, especially the main theme, which is reprised multiple times and comes to a spectacular crescendo in the wedding scene.
Faux Symbolism: On the commentary, Emma Thompson praises the symbolism of Brandon giving Marianne a knife when she's gathering reeds. She cheerfully goes on that she doesn't know what it symbolizes, it's just good symbolism.
Watch Imelda Staunton (Mrs. Palmer) interact with Emma Thompson in this film, then follow it by watching their characters interact in Harry Potter and the Order of the Phoenix. You might never look at Dolores Umbridge and Sybil Trelawney the same.
Hugh Grant and Emma Thompson play siblings in Love Actually. Emma Thompson is also married to Alan Rickman in the same movie.
Hugh Laurie playing sarcastic Mr. Palmer years before House. And stealing the show.
Jerkass Woobie: Although Lucy Steele is possessive, selfish, and full of Sugary Malice, there are several subtle indications in the film that she's even worse off than the Dashwood girls. Her clothing isn't as nice, when Fanny kicks her out she ends up alone on Mrs. Jennings' doorstep crying to be let in, and she has no other connection by which she could find a man to marry. Her treatment of Elinor is still wrong, but it's somewhat understandable.
Values Dissonance: In the movie, Colonel Brandon was forbidden from marrying his cousin Elizabeth because she had no money. In the book, she was forced to marry his brother specifically because she did have money - and it had to stay with the oldest son to keep it in the family.