[kunfuu]

Markdown isn't plain Unicode text. It mixes markup marks with plain text, and is intended to provide more layout than plain text. Plus, the question is rather broad, as there are so many non-alphabetic languages around the globe. I'm not knowledgeable enough to offer an answer.

You may want to read the work by W3C[0]. Some requirements mentioned exceed the needs of simple written communication, but not all in my experience. The problems usually arise when you mix different scripts.

[0] https://www.w3.org/TR/typography/

EDIT: clarifications.