These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Harry Potter and the Chamber of Secrets
Angst? What Angst?: Ginny despite Tom Riddle's Mind Rape, is described as perfectly happy soon after being rescued from the Chamber of Secrets (or at least, in Harry's POV). This is either because Ginny is a Type A Stepford Smiler, or Harry really is oblivious to her suffering. Or the fact that being rescued by Harry is what she wants most. Also see All Is Well That Ends Well.
On second thought, only true in the film. In the book, Ginny is crying from the climax to the middle of the next chapter. Harry doesn't appear to be oblivious, he leads her to adults who can comfort her better than he can.
Well, when Ginny's awoken in the film, she sounds like she could be in shock. She's not crying or stuttering like in the book, but it was probably best to drop that. On a simple practical level, there are very few child actresses who could pull off that level of emotional intensity, especially without it ending up as Narm. (Of course, there's still the fact that she looks all cheerful in the ending feast scene, which presumably occurs later the same day.)
Also, Harry is rather oblivious to her - by his fifth year, he'd forgotten (albeit briefly) about the fact that she was possessed at all, while she indicates quite clearly that she was far from unaffected.
In his relationship with Ginny, it's easy to see Tom Riddle as a kind of metaphorical Internet predator. J. K. Rowling herself acknowledged in an interview on the DVD of the movie that the diary is really a lot like an Internet chat room, but said she hadn't been in one at the time she wrote it so it's just a coincidence.
Rowling has also said her inspiration was the fact that she found diaries to be really scary, as a person's deepest darkest secrets are hidden in them. So rather than the focus of the danger being on talking to strangers, it's more on playing with something you don't understand.
Fridge Brilliance: Of course Lockhart would happily seize Ron's wand to try to cast a Memory Charm on him and Harry, of all of Ron's teachers, he's the only one that wouldn't have a clue that Ron's wand has been broken all school year because he's the only one who hasn't been teaching any actual magic.
When Harry first sees Ron's room at the Burrow, Scabbers is curled up asleep in a sunny spot. Real rats warily avoid direct sunlight, as it's too bright for their dark-adapted eyes and makes it easy for predators to spot them. But Scabbers has a human's preference for light.
Genius Bonus: The bronze statue of a boar that has a prominent place in the Hogwarts entrance hall is a copy of Il Porcellino, a famous statue in Florence, said to have magical powers.
The original Il Porcellino figures in one of Hans Christian Andersen's lesser known fairy tales, The Metal Hog, in which it comes to life and tells a poor street urchin that he is destined to become an artist - not unlike what happens to Harry Potter.
In the movie, after Ginny runs away after seeing Harry, Harry asks "What did I do?", to which Ron responds with "Ginny". No, Ron, that comes later.
It's the Same, Now It Sucks: Sadly film critics other than Roger Ebert talk down to this film for taking a slow paced, Adaptation Distillation approach like the first film. After the third film came out and the tone of the film series changed profoundly, only purists mention this one. The book is also given very similar treatment.
It Was His Sled: There's a Basilisk in the Chamber of Secrets. Tom Riddle is young Lord Voldemort.
Jerkass Woobie: Filch qualifies when his cat, Mrs. Norris, gets petrified. Also when it turns out he's unable to perform magic despite being wizard-born. No wonder the guy hates Hogwarts students so much.
Lucius Malfoy's plot in the second book amounts to this. Arthur Weasley is going to pass some law that makes it harder for him to be evil. So he puts in an old Dark Arts object cursed by Voldemort himself into Ginny Weasley's cauldron. He rids himself of evidence of his genuine loyalty to Voldemort and compromises Weasley's reputation when his own daughter gets possesses and attacks students. Oh and he uses that to get Dumbledore dismissed from Hogwarts. Even when Harry unearths the truth, Malfoy points out that he has no real evidence to pin the blame on him. Unfortunately for him, Voldemort returns and he finds out what happened to that diary he gave Lucius for safe keeping and as a sign of the latter's loyalty. It also contained Voldemort's Soul Jar but Malfoy didn't know that.
Then there's Lockhart's attempt to destroy Harry's mind—and Harry's obviously the only person who can stop the monster and save Ginny—simply because He Knows Too Much.
Narm: In-universe, Dudley's ass-kissing compliment to the Masons ("We had to write about our hero at school, Mr. Mason- I wrote about you"). Harry hides under the table to conceal his laughter from the Dursleys.
Nightmare Fuel: J. K. Rowling received several angry letters from readers who weren't able to finish the novel because they were too scared to go on reading.
The serpent's voice is quite disturbing in the audiobooks.
They Wasted a Perfectly Good Character: One Mugglenet book suggested the basilisk to be this. It's apparently intelligent, centuries old, and Harry can understand its speech, but it only shows up at the end and mostly acts like a generic monster, rather than giving the audience any signs of even being a character.
Ernie "They say the real reason You-Know-Who was after Potter was because he didn't want another Dark Lord competing with him.
What an Idiot: In the film, Lucius Malfoy attempts to cast the killing curse on Harry right outside of Dumbledore's office.
Woolseyism: Voldemort's Significant Anagram name, revealed in this book, in the original was Tom Marvolo Riddle, an anagram of "I am Lord Voldemort." Translations changed various parts of his name; for example, in the German version, his name was Tom Vorlost Riddle, which becomes "...ist Lord Voldemort" (is Lord Voldemort). Something is gained in the German version particular here, as his middle name sounds an awful lot like Verlust, meaning "loss," which applies to Voldemort in a variety of ways.
Other languages aren't quite so lucky. Just ask Tom Elvis Jedusor, of the French translation.
Or Romeo G. Detlev Jr. in Denmark (The G. stands for Gåde = Riddle)