I don't believe Facebook works properly with fragments in URLs. Fragments (the #123 ids) are only visible by browser to 'jump' to a section on a page.
I don't know Kunena's template file off the top of my head. What you should be able to do though, if you can find the full URL to the post, is something like:
{JFBCLike href=http://yoursite.com/forum/board-1/8.html#Post_ID}That will generate a Like button for each post and *should* have a unique URL. We/you'd need to check the output HTML and make sure it's right, and then test that each Like button works how you want.
The things to note, and where I think things could go wrong:
* The post in a user's wall would use the title/description for the page itself, not the post. There's no way to specify a title/description per Like button.
* You would still hopefully have an individual Like count per post though.
* The link in a feed post back to your page may have the # encoded strangely, which would make it not 'jump' to the right post
Just some things to be aware of, but hopefully, you can get it going. If you have any questions, just let us know. If you get it going, please feel free to share the code you implemented, we'd love to take a look and possibly comment on it!
Thanks,
Alex