[ambivalence]

Markdown is plaintext so you decide what it means. I personally write *italic* and **bold**, so I can use _underline_. Most Markdown to HTML converters would make the last example into italic, but you can customize many of them.

Commonmark doesn't even mention "bold", "italic", and "underline". It just says "emphasis" and "strong emphasis". You can style it however you want.

[paulryanrogers]

This kind of undercuts the advantage of a semi-universal format. Though I'd agree underscore wrappers are quite reasonable and natural.

[ratorx]

Markdown isn’t really meant to be a universal markup format. Its primary goal is to document conventions of annotating plain text which keep the plaintext semi-consistent and readable.

So the purpose of , * etc is purely emphasis. If you need to represent something specific (bold, italic etc) then that’s a job for the Markdown parser (or embedded HTML etc). The result of the parser (HTML, etc) will be less human readable, but actually able to specify formatting.

I agree that CommonMark could be extended, but I think the focus should be on semantic* relevance rather than markup specification.