SO after some more testing on my and some other plurkers part, we're pretty sure that despite Plurk allowing us to put in @font-face into the code, it just doesn't load custom fonts for rendering.

So no dice, y u do dis plurk.

IN THEORY, one way to get around this would be to use a Stylish stylesheet to override plurk, but it'd basically on work on your end and other users won't be able to see the fancy font.