So what safeguard from a person looking to hurt someone from doing this to an old post
That's a different problem, yes. There's this:
However, that is not nearly adequate. A moderator does not see what has changed. Also it could be used as a timed-attack. Insert it now and report in 2 years. That is another reason why this thread is bullshit. Imagine if we just banned you forever, philipma1957, because you plagiarised some random post 6 years ago?