When someone makes an edit that is improved by a reviewer is he or she notified of the fact that the edit was improved?
The only notification a user sees is a
+2 in the Achievements at the top bar next to Inbox entry (provided that the user didn't down-vote more than two times before the edit was approved, in which case the user many times don't get to see such
+2 unless s/he tap that icon).
[It] only makes sense to accept and improve this if the editor is notified of the fact that his edit was accepted without editing, as otherwise you would be blindly rewarding incorrect behavior.
The phase of learning is dependent on the curiosity and willingness of the editor to learn and improve himself from his own actions and its reflections. Enough with the riddle, the point is that the user can always tap that
+2 and click on the entry (be it Question/Answer) to see who approved it or what exactly happened to the edit.
I made more than a hundred of suggested edits before reaching 2k+ on Android Enthusiasts, and it never ever happened that I forgot to check who reviewed my edit and were there any mistakes left that were corrected. Furthermore, during that period I always kept my eyes on the Active tab and always visited most of the changes taking place on the posts, including the ones I suggested the edit with. In that way, I was always aware of my scope of improvement.
That said, I wish that an option for informing the user with a custom message should be there for the reviewers when improving an edit, thereby agreeing with you. My reason to agree is, there are times when the edit is close to be superfluous, like correcting grammar/typos in the whole body (a question with one paragraph) but missing the first line as well as the vague title, something that shouldn't be missed by anyone. But you can't really reject that edit because it is helping in readability for the rest of the body.
Some other times, you see edits which fixed the links which were obsolete or incorrect, but avoided the dire need of formatting of the post. Again, there is no point in rejecting such edits either because they are helpful. And there are many more cases that one can mention here.
It is at least certain to me that if the user isn't curious or willing to improve rather swiftly s/he possibly won't come to know what were the critical things left in that edit and should be fixed from then on in next edits. The Suggestions tab is embedded under Activity -> all actions, something I don't find very helpful when learning of a user is concerned. I came to know about this location only through a question on a Meta site, after gaining 500 points!
But I still try few things. Whenever I improve an edit I always leave a comment in the revision like "made corrections missed by the last editor", "fixed XYZ left by last editor", so that at least somebody else might learn something if not the intended user.