Esoteric Happy Ending: Many readers take the news of Frank Churchill and Jane Fairfax's marriage the way Mr. Knightley does, which is to speculate that for all of Frank's apologies, her happiness with him is still very much in doubt.
Emma's ignorance of Harriet's rank and insistence that the circumstances of Harriet's birth should not deprive her of the same respect and opportunities open to richer, less tender-hearted women is portrayed as a bad thing. In at least one adaptation, Emma lets her imagination run wild and assumes that Harriet's mysterious father is a member of the royal family! This is why she thinks Harriet is suitable for Mr. Elton - not because rank doesn't matter, but because she's imagined a much more illustrious background for Harriet than is plausible. Mr Knightley's objection is probably because it's not fair to delude the rather simple-minded Harriet into believing that she doesn't have a problem... in fact, more to the point, to do so while derailing her marriage to a yeoman with whom she would have been perfectly happy. (Even to the yeomanry it would have mattered, albeit not as much — Robert is still a catch, even if he does get his hands dirty.)
It's eventually revealed that Mr. Knightley has been in love with Emma since she was thirteen... at which time he was twenty-nine! Though he says it in a tongue-in-cheek-y way.
The book's portrayal of "gypsies" is very wince-inducing now. Not only is that term used freely (which some consider very politically incorrect, but some Romani consider it fine and refer to themselves with it as well), but they only randomly show up once as a threat from which Frank has to save Harriet, and are portrayed as a faceless Always Chaotic Evil group.
The Woobie: Miss Bates is pretty annoying for most of the book, but you want to give her a big hug after Emma insults her.
The Woobie: The 2009 miniseries gives us a glimpse of the Bateses' elegant home just before they had to leave (and before their beloved Jane is sent away), so the viewer gets a better sense of the sacrifices and pain that Miss Bates has had to endure.