Thanks for the contribution. I can totally see the logic for Japanese and even some of the Latin punctuation here, but I'm a bit worried this goes too far and will start catching false positives. In particular depending on the Markdown rendering in use it might be part of the requirement for these markups to have some space or other separator first. This avoids things like a clause,* more text where the asterisk might be a footnote marker or otherwise be literally rendered to not be mixed up with emphasis markup.

We need to look into how Pandoc, CM, GFM, and others handle this first and make sure we at least move closer to that handling and not farther away from it.