' there is a big clue in the film, i have a hard job covering all the clues up, this one is very important'
I read it a long time ago, and don't have a link.
In every book so far we have been told by hermione
'How many times do i have to tell you, you can't apparate inside hogwarts, it says so in hogwarts:a history'
And what does dobby do in the hospital wing after he bewitched the bludger.... he apparates.
he doesn't just make himself invisible because harry is clutching him... and then clutching thin- air....
So i think house elves being able to apparate and disapparate inside hogwarts will become quite important in future books