I've deleted my FB account several years ago, but this is what I remember: There was a note like "Bearbeitet" ("changed") right in the post header, when a post had been changed after initial posting. You could click on that and see at least one previous version of the post.

A note like this, with a changelog, should therefore be fine for twitter and counter all "I never posted sth. like that!" talk, as it would be easily to be debunked.