@rxliuli CommonMark prioritizes compatibility with Markdown, so unless a change is designed to have minimal impact to the existing large corpus of documents written in it, I doubt a solution for CJK will get incorporated into CommonMark.
My sense is that it is difficult if not impossible for a single static lightweight syntax (be it CommonMark, Asciidoc, RST, or whatever) to support languages with such different natural syntaxes (i.e. the syntax of the natural language as written). For example, Markdown’s emphasis markup is designed specifically for languages with space-delimited words. If you change it to work better for CJK, it will work less well for space-delimited languages.
It would make more sense to design a new markup language oriented for the CJK language group, or perhaps dedicated ones for each of those languages since, as @barro350 suggests, they have significant differences between them as well. I only know Chinese so I can only guess.
I’m working on a solution (Plain Text Style Sheets) that makes it easy to declaratively define custom syntaxes or extend existing ones like CommonMark, and I will endeavor to offer an option tailored specifically for CJK languages. I’d need help figuring out what all the needs are. Anyone who considers themselves an expert feel free to drop me a line.