This doesn't really make sense, for a couple reasons...

There are many flavors of markdown. We'd need a standards body, compatibility suites, etc., and for all the browser vendors to adopt it.

Meanwhile, markdown is designed to transform to HTML, which browsers already render. Adding a markdown-to-html plugin/step to your web server or publishing process is not exactly the most burdensome thing, relative to everything else it takes to develop, publish, and maintain a site. And it resolves the markdown flavors issue.

The thing is, people could choose to publish, simple uncomplicated sites now -- it would be cheap and easy, too. The HTML is barely more complicated than the equivalent markdown, and it would take a few lines of CSS to apply a basic style.

The many sites that choose to be complicated, cluttered, and expensive will continue to be so, for the same reasons they are now. Markdown would just be another way to build simple sites, which they don't want.

It's very similar to the Markdown syntax we all know and love/hate, but fixes many inconsistencies in the spec, and also makes it possible to parse a document in linear time, with no backtracking. It is also much fuller-featured than commonmark, with support for definition lists, footnotes, tables, several new kinds of inline formatting (insert, delete, highlight, superscript, subscript), math, smart punctuation, attributes that can be applied to any element, and generic containers for block-level, inline-level, and raw content.

Some examples, showing how Djot would be rendered into HTML: https://htmlpreview.github.io/?https://github.com/jgm/djot/b...