Evan Solomon

Comment forms allow some HTML, this plugin extends that to let users type in <a href="http://daringfireball.net/projects/markdown/" rel="nofollow ugc">Markdown</a> and have it automatically converted to HTML. It also extends Markdown with a couple features made popular <a href="https://github.com/github/github-flavored-markdown" rel="nofollow ugc">by GitHub</a>. Conversion from Markdown to HTML is completely automated and doesn’t require anything on the commenter’s part.
The feature additions from GitHub are:
<ul>
<li>Single linebreaks are treated as new paragraphs</li>
<li>Code “fencing” with three backticks (“`)</li>
</ul>
Two notable features from GitHub’s Markdown implementation are missing:
<ul>
<li>To do lists: Doing these well would require some front end interaction, which I decided is outside the scope of this plugin at least for now</li>
<li>Repository autolinking (e.g. comments, issues, etc): These seemed a little too GitHub-specific.</li>
</ul>
GitHub-Flavored Markdown Comments is developed, unsurprisingly, <a href="https://github.com/evansolomon/wp-github-flavored-markdown-comments" rel="nofollow ugc">on GitHub</a>.

GitHub-Flavored Markdown Comments

WordPress plugin to let commenters use (GitHub-flavored) Markdown, and turn it into HTML.

GitHub-Flavored Markdown Comments vs Static Site Exporter