I am so sorry for the delayed responses. In August, I remember testing the page you listed and I couldn't find an issue. I missed your post from the end of September somehow, but in testing it now, I'm not seeing an unencoded characters showing up in posts.
I've tried in both the Facebook Debugger (
developers.facebook.com/tools/debug) and by pasting the URL you posted above into a status update on Facebook itself. The preview in both shows, what looks to me, like well encoded and properly looking characters.
Can you let us know (or post an image of) what you're seeing? If you can, try to create a new post as well. If it works with new posts, but not older ones, that could be an indication that either Facebook fixed something on their end or that there's some sort of caching issue with Facebook where a post initially has unencoded characters but eventually resolves itself.
Thanks,
Alex