Content of collapsible sections (...) renders markdown in GitHub repo but not on GitHub Pages

Question

On the GitHub repo the README, the markdown inside the collapsible section renders as desired.

But on GitHub Pages the markdown is not rendered, just literal.

The _config.yml is essentially empty.

In the issue is mentioned Markdown inside and not being processed, and the suggested fix is:

markdown: kramdown
kramdown:
  parse_block_html: true

That does indeed fix the rendering of the content, and I am fine with switching to kramdown, but it breaks the rendering of <details> and <summary> and the twirl-down. (So I rolled it back.)

The relevant HTML and markdown is:

<details><summary><strong>About transliteration</strong></summary>

About half of the billions of internet users speak languages written in non-Latin alphabets, like Russian, Arabic, Hebrew, Chinese, Greek, Armenian and Hindi.  Very often, they haphazardly use the Latin alphabet to write those languages.

`Привет`: `Privet`, `Privyet`, `Priwjet`, ...  
`كيف حالك`: `kayf halk`, `keyf 7alek`, ...  
`Բարև Ձեզ`: `Barev Dzez`, `Barew Dzez`, ...  

... ... ...

</details>

Is there a way to force the rendering without kramdown (and without using raw HTML)? Or is there a way to make a collapsible section with kramdown?

The full repo is of course up at github.com/deepchar/deepchar.github.io.

Answer 1

As noted in the comments by Waylan, markdown in GitHub repos like a README.md are rendered with Commonmark.

The repo github.com/github/jekyll-commonmark-ghpages#installation mentions that support for GitHub Pages is on the way and gives some instructions.

Installation

Add the following to your Gemfile:

group :jekyll_plugins do
  gem 'jekyll-commonmark-ghpages'
end

and modify your _config.yml to use CommonMarkGhPages as your Markdown converter:

markdown: CommonMarkGhPages

This processor is currently in testing for use in GitHub Pages.

To specify extensions and options for use in converting Markdown to HTML, supply options to the Markdown converter:

commonmark:
  options: ["SMART", "FOOTNOTES"]
  extensions: ["strikethrough", "autolink", "tables"]

To make it work (as of October 2018), all I had to do was add markdown: CommonMarkGhPages to the _config.yml. (There is no Gemfile in the repo.)