Now try doing the same with CSTML, in applications that so support HTML.

Now consider how little that markup contributed to the semantics of the text here - most of it can be stripped and the text retains it's meaning.

Then consider how long it took for HTML to percolate through these applications despite HTML - unlike CSTML- having universal utility.

And here's the thing: As someone with a history of writing compilers, parsers, language tools over 30+ years, CSTML is too verbose for me to want to use even for tooling. It's way too low level even as an internal representation for tooling.

It also still doesn't help: You still will need a compact textual representation anyway so people can represent it in contexts where the tooling doesn't exist, or can't exist, such as paper and handwriting, and speech.

All I can do is encourage you to try. If you succeed, great, and if not you will understand the difficulties involved.

I've tried the custom syntax representation (though I used XML which saved me from writing a custom parser) - it turned out to just be an obnoxious detour. I tried syntax aimed at removing ambiguity in round-trips, and it sort of worked but got too verbose. I tried a purely visual approach, and hence why I'm so insistent you need to be able to roundtrip to text. I spent years trying things and looking at others attempts.

I'd love to be wrong, but I very much don't expect any big breakthroughs in this area in decades - the attempts I keep seeing keep repeating all the same mistakes with few signs of lessons learned.