Note that most "no" commenters said that correcting stuff like spelling and grammar is OK, but style changes not - maybe part of the "yes" voters didn't read to the end of your first post, and thus didn't even notice it was about substantive changes?
Or maybe I'm just a bit biased because I think it's a bad idea.
I was put off posting a review for one novel I'd read, because the author (just a few weeks or months after first publishing the book) did a revised edition. I did not read that one, but I saw that they had added a prologue that had not been in the book I read. The revised edition is a different book from the one I read, so my review might not apply to it.
I'd think fixing mistakes like spelling, grammar, eyes changing colour, or other things where usually you only have to change a word or a few in a sentence, are OK. Or rewriting a sentence here and there because it came out wrong and says something you did not mean to say.
Fixing big plotholes or adding subplots or a complete rewrite to change the style... Well, maybe if the book is over a decade old and you really want to revisit it. Stephen King did that with <i>The Stand</i>, and Terry Pratchett with his first novel, <i>The Carpet People</i> (with 20 more years of practise). But a book that's a few months old? I'd be for moving on.
(Since someone mentioned serialised fiction: I think it would be different there. A serial posted on a blog and a collected-and-edited ebook would be two different editions. I'd hope the editing would include stuffing plotholes.)