Following the suggestion in response to my support request, I've made a quick patch to JLJ and am posting this test post to see if it works correctly.
A correct fix would probably require taking a look at the API documentation for the
&ver= field and taking a look at JLJ; I suspect that said setting should only be set if the current locale is a Unicode locale, rather than always turning it on as I currently am, but I'd want to know how it's defined to be sure.
Anyway, here's the test text again, using the full toolchain with patched jlj; hopefully for the last time.
The problem was presumably due to an extended character in either the name "Métro Bis" or the dessert "Crème Brulèe", possibly the name "Métro Bis" being present in the post title.
If it works, I'll be crossposting to LJ to confirm correct encoding there.
Edit: Confirmed, I can edit this entry and crosspost it.