This is picked up from a discussion on Book 5, but don't worry- there are no spoliers here!
The american editions are editted slightly so that american readers will understand them- words like " skip " are changed to "dumpster " and backwards and forwards become " backward and forward. " The children stop "going to the toliet" and start "visiting the bathroom."
Fine, it this helps people understand.
BUT
They ARE BRITISH SCHOOL CHILDREN!! If their characters are to develop fully they need to be left uneditted- small changes can make a big difference, and can change the feel of the book.
To give another example- Catcher in the Rye. This was originallt editted for a british audience , so that " ass " became " bottom " etc.... This is AWFUL!!!
Imagine if instead of saying "mate" they said "buddy" ....
I have listened to the Audio books, and the american editions are changed just enough to alter the feel of the book... URGHHHH.