This is why we encourage people to mark their edits -- like this

EDIT (or UPDATE, etc): (concise summary of the change)

in the edited node and to use strikeout if they wish to disclaim something previously posted.

No downvote for this suggestion but I do (and you're encouraged to) consider the changed node for restoration of the original content if it's been deleted ... and I also do, at least occasionally, downvote a node when I know it's been substantially changed without a note making mention of the edit.