I sometimes link to topics/posts others (and I) have made on social media, so it's something to link other than the index and can highlight the good content.
I never have; mainly because I never really thought about it. However I can totally see the benefits of doing it. They are technically on your forum so I do not see why anyone 'couldn't' use them.
I didn't know there was such a thing; but it does sound very interesting and could work out in my favor. I might look into it and give it a shot sometime. 😀