Based on the rules for editing code under review, I would like to recommend this feature.
The goal of code review is to improve my submitted code, and for others to learn from the improved code - I would like to provide an updated version back to the community.
I could do this by simply editing the original post but that causes us to lose the original code in question and the community recommendations no longer have the right context (not to mention that is not allowed on the site - and rightly so).
I could post the updated code back as an answer to the post or as a new question but, imo, that gets too noisy and difficult to track.
I would like to see something like tabs or links at the top of each code block that would allow me to track and post various versions of the code in order to show how it has changed based on the reviewers feedback - showing how the code evolved overtime. I think this would provide a lot of insight and very useful. Each 'version' should also allow me to credit specific reviews who helped refactor the code.
Another alternative (actually should be in addition to above idea) is a link within the code that pops up when there are various diffs for a section of code.