Add ability to add change comments after saving

Sometimes an edit is made quickly and only after hitting the "Save" button do you realize you wanted to comment the change you made. It is currently not possible to add change comments for a particular change after saving the page.

I understand that not being able to edit existing change comments is important for auditing purposes, but I don't see any reason the person who last edited the page could not add a change comment to the latest change? Or why not even earlier changes... The condition being that users can only add comments to changes that have not already been commented.