If you try to do it, you will get something like this:
Look at the description: it's not very "facebook friendly", it doesn't communicate what you want.
Look at the image: even if you customize it, if you share a different thread from this board, the image will be always the same!
Don't you think that it's better something like this?
If you are preparing a simple html page, it's very simple to do it: you just need to write what you want inside the og:description and og:image tags on your <head> of your <html>.
What I suggest is: give the rights to admins (also to mod and users if you want) to customize these parametres!
It can be very simple: two input boxes inside the new thread/edit thread page!
Thank you for your attention.