HARRY POTTER....I can't help it!

I'm re-reading the whole Harry Potter series.  I'm currently on Book 4 and thoroughly enjoying reading the series again.  I especially like the fact that I'm reading it a second time almost as soon as I finished it the first time.  There's so much I missed.  I'm finding that it feels as if I'm reading it for the first time because of all the details that are jumping off the page at me now. 

But I am finding myself marking a consistent grammar error throughout the series that is really starting to drive me absolutely insane!!!  Rowling misuses singular indefinite pronouns and their modifiers!!!  It's driving me crazy!  I could have let it slide with the first 2 books, but the deeper the series goes, the worse it gets!  After getting the feel of things and knowing her series was well received and well loved.......considering the fact that Rowling is BRITISH--the British are famous for being strict grammarians!!!.....after having editors read through the series....and what about the screenwriters who use the incorrect singular indefinite pronouns?!

Now, maybe, just maybe, in the true English (British, I mean) translation, Rowling uses singular indefinite pronouns correctly and it's actually the American translation (we all know that there IS a vast different between the book released and read in England and the book released and read in the US) that is making the mistakes.  Regardless of the excuse, there is NO excuse!!!!!  It's one thing if the kids in the story use the pronouns incorrectly, but to have PROFESSOR MCGONNAGAL use singular indefinite pronouns incorrectly in simply inexcusable!!!!!!!