I wish Asciidoc was more popular
Very briefly on admonitions: there is nothing stopping you from adding them to markdown yourself:<p><pre><code>    <warning>
    You _really_ shouldn’t
    play with matches, Debbie.
    </warning>
</code></pre>
Later on in that document:<p><pre><code>    <style>
    warning {
        display: block;
        color: red;
    }
    </style>
</code></pre>
Which is a very long winded way of saying that you can use markdown for authoring actual content, and then use good old HTML for styling whatever else you want to.<p>Relying on asciidoc for styling elements like admonitions always felt like the wrong tool for the job.  Like writing a Java generator in Perl, instead of just writing actual Java.