The way I've always wished this could be implemented is a "Show original" button for edited notes. It is a much more general and productive use case - not only to retract or disavow but also to correct typos, add extra content like pictures, mentions, links to sources, etc.
Discussion
Another feature I've always wished existed is the ability to jointly own a post or note. That is, that whoever first posts it, can add other users as editors/owners, so they can modify the note too. Following this line of thought, the "Show original" button could actually be a "Show version" button, like you have when you share a document on Google Docs and such. Maybe this one requires a dedicated type of event or/and client, of course.