[sciurius]

As you found out, there is no such thing as 'standard markdown'. Well, there is John Grubers original implementation but this is generally considered too limited. So there are many non-standard 'extended' versions (not unlike ChordPro). It seems that nowadays the GitHub extended version of markdown (GitHub Flavored Markdown, GFM) is very popular, but even GFM cannot change the text colour and highlighting unless you resort to its HTML extensions.

So for ChordPro we basically need to create our own markup, possibly a markdown-like variant. The only thing we want is to tweak in-line text appearance. Everything else (headers, paragraphs, lists, etc.) is not relevant for ChordPro. Since we are dealing with lyrics texts there is a much bigger choice of 'special characters' than in general purpose texts, but many different markup characters are hard to remember.

Personally, I'd still opt for something simple but flexible like {style text...} or <style text...>, where style is either predefined (e.g. em, strong, ul) or —in the case of the ChordPro application— one of the defined font styles. Multiple styles can be combined with +, e.g. <strong+em text...>.

What do you think?