This is a really good article on editors and the posthumous alteration of texts, usually without the permission of the deceased author. There are a surprisingly high number of examples. It's occasioned, of course, by two high profile examples - the newly published original versions of Raymond Carver's short stories, which I've written about on here before, and the 'new' Nabokov, the one we've known about for years, that Nabokov said should be burned. It's finally being published. Is that a good thing?
Probably not. If Nabokov wanted it burned it's probably because he knew it wasn't publishable. Maybe it could have been if he'd lived long enough to work on it, but he didn't, so it shouldn't. I don't think it should have been burned either, but it could easily have sat in whichever library has Nabokov's paper, available for researchers because there will be some insights into the author to be had from it, but not published and tarnishing his reputation.
As I said, it is surprising how many books were changed after an author's death. I didn't know that Billy Budd was unfinished, for example: it was finished by Melville's wife and editor. And I didn't realise that there are two versions of Tender Is The Night in circulation, in which the order of the three sections is different.
I can't help thinking there is a great movie in the Carver/Lish thing. Because writing is everything to a writer, Lish's radical cuts and Carver's dislike of them feel almost like a fight over the man's soul.