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Apropos of nothing - a random HP thought.
Where does half the fandom get the impression that Harry is cheating by using a book with notes in it?
They are allowed to use their book while brewing and are supposed to have read up on the potion they are preparing in class.
And in written tests, I doubt they are allowed to use their books anyway, so the notes won't be any help to him there.
The only difference I see between Harry and a Ravenclaw (in this instance) is that the Ravenclaw would have made the notes himself - and probably not in the book, but on a spare bit of paper.

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Except for Snape. He did have to hide it from Snape - but that was because of the fact that 1. Snape hates him and would use any excuse to confiscate the helpful book and 2. he'd learned some dark Jinxes from the book, which he wouldn't want to admit to having done.