Rowlings sentences are chock-full of clauses and phrases, comas and semicolons, some stretching out to 50 words!
Well, yes, there are indeed characters who are in comas--Neville Longbottom's parents in particular, if I recall correctly. Not sure that qualifies as "chock full" however.
Oh, and it's no surprise, but I endorse the position taken on Harry Potter--do go out and read them all if you haven't. Or if you haven't recently.