If I have to write "paragraph" at the start of every paragraph I'll immediately start looking for some kind of a meta markdown tool to make it easier to write.
From the glorious https://en.wikipedia.org/wiki/DocBook :
<chapter xml:id="chapter_1">
<title>Chapter 1</title>
<para>Hello world!</para>
<para>I hope that your day is proceeding <emphasis>splendidly</emphasis>!</para>
</chapter>Implementation details still have to be implemented. Someone else might come along and figure that different documents may want to interpret "emphasis" differently, and while we're at it, why not make it composable? They may design a DSL for that, and give it a cool name too, like "cascading style sheets".