As you may notice, there's now a Facebook icon in the bar above the reply box (if using full reply, not quick reply!), all you need to do to show a Public FB post here, is click the button and paste the link to the post (right click the post and copy link).
Note that it needs to be a public post, not to a private / closed group, so for instance a photo status change is public, whereas a post to a secret / closed group isn't
So the link to the photo being changed by Su is (spaced so teh forum doesn't try to render it!):
h t t p s://www.facebook.com/photo.php?fbid=10153512912100670&set=a.430119620669.231655.730425669&type=3
so click the FB button and paste, you get:
