Thank you for the update. We’re self-hosted for Discourse, in English, and Facebook links pretty consistently (I want to say “always”, but I’m not 100% sure) display in Cyrillic. 
I want it to be something on our side that we can fix, but I fear you’re right, and Facebook does what Facebook does. 
I’ll keep digging into our situation, just in case I can find a bit to swap. Thank you again!