Often an edit to one of my questions or answers will make it a lot better. The edit can constitute more to the site than someone posting another answer or comment.
Some users make quite a lot of good edits and are awarded the Strunk & White and Copy Editor Badges.
However, there is no incentive for people to edit well.
So, as the person that posted the question/answer, let me mark the edit as useful or very useful, and then reward some rep to the person that did the edit.
I don’t think we need a full voting system on edits. That will just make the sites more complex.
@[editor] - thanks for the edit, made it a lot clearer