forum shares direct message which is not adressed to it
Create post with clicking on lock icon and in permissions choosing Custom selection and choosing a contact, that contact sees the post two times. The top one is expected and is seen also in direct messages, the second one is not needed.
(images missing due to issue #1509 (closed))
Actually, I can see the second post under different connected account because it is public post about the private one :-)
(image here on the same site is not showing right due to permission but the post does)