(apologies if things break when I test this in a few moments)

the answer appears to be "it displays it horizontally anyway"

Does it work inside a toot itself:

test ᠴᠣᠷᠢ ᠶᠢᠨ ᠭᠠᠭᠴᠠ ᠪᠣᠰᠤᠭ᠎ᠠ ᠪᠢᠴᠢᠭ᠄ ᠮᠣᠩᠭ

::<

I would love to see the alternate universe where top-to-bottom in columns going left to right writing systems dominate, where wikipedia looks like this:

(from the Mongolian Script wikipedia page)