Every once in a while a situation happens where I accept a review and then some other discussion happens that results in a couple of extra iterations on that same review.
If I'm then asked to look over the changes again it would be neat to have the option to show only the changes since the last time I accepted a revision. Obviously there's a manual way of doing it, but that requires me hunting down the revision that I last accepted, which isn't obvious. All this request is really asking is some sort of UI that allows me to quickly select the revision to diff against.