Markdown uses # for headings, ex: # This is H1, ## This is H2.
The problem is that Bulma doesn't style headings based on HTML tags, but classes. Markdown generated file is <h1>This is H1</h1>, but you need to use <h1 class="title is-1">This is H1</h1> to make it look like heading.
Currently it's impossible to use markdown - headings dont work.
Use content:
https://bulma.io/documentation/elements/content/
A single class to handle WYSIWYG generated content, where only HTML tags are available
<div class="content">
<!-- Generated markdown here -->
</div>
Thanks @robbinfellow
Most helpful comment
Use content:
https://bulma.io/documentation/elements/content/