Harry Potter and the question of author rights

Photo courtesy: Warner Bros

JK Rowling has recently gone on record saying that she regrets the relationship between Ron and Hermione. Obviously, this has caused quite the uproar amongst Harry Potter fans. You can read The Guardian article here. 

What do you believe is appropriate in terms of authors commenting on previously published works? Is it fair (as well as useful) for authors to divulge information about a storyline that has been completed and is, quite literally, a "closed book", or is it, in fact, damaging to the fans and plot? How much say-so should an author have once they've given their novel to the people, and do you find it innately damaging for the writer to change their mind about a plot/character, publicly? It's an interesting concept, and one that doesn't have a readily apparent answer.