[alangpierce]

Unicode and Punycode were originally designed for letting computers handle the wide variety of human writing systems, common ones like Chinese and Arabic, as well as rarer ones. Much more recently, the emoji characters were added to that same Unicode system, so any encoding system these days that's international-friendly also ends up supporting emoji as well.

So Punycode wasn't specifically designed to work with emoji, it just happens to work with emoji because emoji are part of Unicode.