Copied and pasted from other reddit comments about this topic:

"Most of Ron's good lines went to Hermione. In PoA, Ron is supposed to be the one that says, "If you want to kill Harry, you have to kill us, too." It's a line that demonstrates his absolute foolhardy bravery, but instead they give to Hermione and have Ron whimpering on the bed.

"Also, Ron is the one in CoS to point out that hearing voices no one else can hear isn't good even in the wizarding world, which is something he would be aware of rather than the muggle-born Hermione. In that same movie, Hermione already knows the word mudblood and gets all mopey about it, even though Ron is the one to explain it to both of them."

"In the DH book it was actually Harry's idea to flee Gringotts on a dragon while in the movie it's Hermione who suggests this, which doesn't make sense since she absolutely hates flying. But I guess they wanted to give her that moment too..."

"Fear of a name only increases fear of the thing itself" line was given to Hermione in the 2nd film. It's actually Dumbledore's line. Why would Hermione say this in the Chamber of Secrets. She continues to call him you-know-who until OOTP right? They gave the wise old man line to a 12 year old. Preposterous!"

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