If posts are editable there definitely needs to be a way to see the original post.
But as for link not displaying right or picture doesn't show up, etc., that is what the preview button is for. That's the point I made above, instead of making a sale thread or something and trying to race to get it done, the preview button beautifully shows how your post will look, pictures, links, etc. and changes/corrections can be made before the mistake occurs.
It does make sense if you forget something, but I think if you start with a short time frame, it will be slowly expanded over time.