I think anyone who's ever written any kind of serious piece knows that editing is hard, irritating, infuriating, &#(*&%*&#ing, etc.
I'm pretty sure, too that more than a few of us have "over-edited" sections so that they're polished to the point you buffed off the luster or the voice has been reduced to a monotonous drone.
So where do you draw the line?
Another way to look at this is to find a novel (preferably one that's popular and you don't like yourself), take part of a chapter and edit it as though it were something of your own. Now compare the voice of your version to the original and see if you can figure out what makes it different.
Is it word choice? Sentence structure? Or do you impart something into the characters 0r plot that you thought was missing in the original?
I've done this, and decided that I can't turn off my internal editor... it's ruining what could be fun reads. A number of books lately qualify as what I'd call "good story/bad writing".
What it amounts to is a writer version of back-seat driving.
When you read a commercial novel, no matter what you think of it, the novel's been edited. Someone's gone line-by-line and found the mistakes and an enormous amount of time and effort to make it the best it can be while preserving the author/character voice.
When you read a book with an eye for enjoyment, that's enough of a polish to make the ride smooth. But, when you read it with a critical eye (this is worse when in "edit" mode on your own WIP), all that registers is a bunch of jerks and stops as the story snags on things you might not think have any business in a published book. It makes it difficult to enjoy the ride.
I've come to the conclusion that voice is like a Jenga tower.
One or two changes can leave you with an edge-of-your-seat, interesting formation with unexpected gaps to give it character. Change too many things, and the whole thing falls apart and isn't any good to anyone.
Hopefully that made sense. Editing's sort of fried me.