What are the biggest plot holes and errors in Harry Potter?

One word: Quidditch.

Not only is the wizarding world strange enough to have only developed one sport, but the single sport that they have also made ZERO sense.

• The scoring system. Score a goal - 10pts. Catch the snitch - 150pts and the game is ended. This is ludicrously unbalanced. 90% of the time the chasers are utterly irrelevant to the outcome of the game. Forget that nonsense going on down below and get me 7 seekers on my team, let's go get that little yellow bitch.

• The crowd. What exactly are they watching? The only thing that matters, catching the snitch, can happen within the stands or a hundred yards out of the stadium! So while I’m watching 6 guys throwing around a quaffle in a finely balanced 40–30, suddenly there's an announcement: “Hey… sorry you couldn't see it… but Potter got the snitch and the game’s finished. Gryffindor wins. Have a safe journey home.”

*THE CROWD CAN’T SEE THIS*

• Harry is Gryffindor’s seeker at the age of 11. If I was a fully grown man of 18 and didn't make the team in my senior year because of a child I'd be pissed. Luckily that would never happen because 11-year-olds have only just started flying lessons and that would be ridiculous. Oh, wait.

• Draco becomes a seeker at 12. Seriously, is Hogwarts that bad at producing seekers?!

• Bludgers. “Sorry Mrs. McWitchface but your son has, unfortunately, died during Hufflepuff v Ravenclaw because a 150lb Bludger struck him in the face.” But then Hogwarts never was one for health and safety.

Muggle-borns at Hogwarts must've been like “wtf is this nonsense, let's go watch some football”.

Update 1: Let’s talk about the Quidditch world cup match between Ireland and Bulgaria.

Ireland wins 170–160 but Krum catches the snitch. What on earth is a professional sportsman, in a World Cup final, doing knowingly losing his team the game?! Imagine a Super Bowl with the Patriots down by 4 with 10 seconds left, it's 4th and goal. What Krum just did was kick the field goal.

The comments saying this game proves chasers are relevant to miss the point - the Ireland chasers shouldn't have won the game and only did because Quidditch’s biggest star is an utter moron.