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.
One of them being a player proposing to the other team's captain after being defeated by her team. She replies by hitting him with her broomstick.
Some of the Obvious Rule Patches are hilarious. For example, you're not allowed to decapitate a Keeper with a broadsword, attempt to murder the referee, or turn a Chaser into a polecat. Yes, Quidditch has rules against that.
Then there's the Marsh Witch's diary, which consists entirely of Tuesdays. The book quips that the onlynote non-Quidditch related interesting information to be gleaned from it is that she seemed to only know a single day of the week.
In the introduction, Dumbledore shares his advice about not mistreating Madame Pince's library books. He once absentmindedly doodled in a borrowed book, and the book retaliated by beating him on the head.
Fridge Horror: The infamous Quidditch match of 1492 broke every rule that has ever been written for Quidditch. As the above states, the rules include "no murdering the referee" and "no decapitating a keeper with a broadsword". There is a disturbingly good chance that these rules were broken.
Paranoia Fuel: Dumbledore can't guarantee that he's removed all the anti-vandalism curses on this book, so treating it roughly may result in Madame Pince appearing in your home and demanding a heavy fine.