Floris-Jan

Simple Markdown is a lightweight WordPress plugin that adds a custom Gutenberg block for rendering Markdown content directly in your posts and pages. Perfect for developers, writers, and anyone who prefers writing in Markdown format.
NEW in 1.3.0: Professional Code Beautification 
* Automatic code formatting and indentation for all supported languages 
* Professional copy buttons positioned as elegant tabs outside code blocks 
* Language-aware beautification (JavaScript, PHP, CSS, JSON, Bash) 
* Smart preservation of ASCII art and tree structures in copy-only blocks
Core Features:
<ul>
<li>Custom Gutenberg block for Markdown content</li>
<li>Support for common Markdown syntax:
<ul>
<li>Headers (H1-H6)</li>
<li>Bold and italic text</li>
<li>Inline code and code blocks with copy functionality</li>
<li>Links</li>
<li>Unordered and ordered lists</li>
<li>Blockquotes</li>
</ul>
</li>
<li>Professional code block rendering with:
<ul>
<li>Automatic beautification and proper indentation</li>
<li>One-click copy functionality with visual feedback</li>
<li>Language labels (JavaScript, PHP, CSS, JSON, Bash)</li>
<li>Tight line spacing optimized for code readability</li>
</ul>
</li>
<li>Clean HTML output with semantic markup</li>
<li>Theme-resistant styling with robust CSS overrides</li>
<li>Easy to use interface</li>
</ul>
This is the core version with all essential markdown features plus professional code handling. A Pro version with syntax highlighting and other advanced features will be available in the future.
Supported Markdown Syntax:
<ul>
<li><code># Header 1</code> through <code>###### Header 6</code></li>
<li><code>**bold text**</code> and <code>*italic text*</code></li>
<li><code>`inline code`</code> and code blocks with triple backticks</li>
<li><code>[link text](URL)</code> for links</li>
<li><code>- item</code> for unordered lists</li>
<li><code>1. item</code> for ordered lists</li>
<li><code>> quote</code> for blockquotes</li>
</ul>
Advanced Code Block Syntax:
<ul>
<li><code>```javascript copy</code> – Beautified JavaScript with copy button</li>
<li><code>```php copy</code> – Beautified PHP with copy button</li>
<li><code>```css copy</code> – Beautified CSS with copy button</li>
<li><code>```json copy</code> – Beautified JSON with copy button</li>
<li><code>```bash copy</code> – Bash commands with copy button</li>
<li><code>```copy</code> – Copy button without beautification (preserves ASCII art)</li>
<li><code>```</code> – Plain code block (no beautification, no copy button)</li>
</ul>

Simple Markdown

Simple and fast plugin to render markdown with a custom Gutenberg block. Professional code beautification and copy functionality included.

Stephen Harris

This plugin allows you to write posts (of any post type) using the Markdown syntax. The plugin converts the Markdown into HTML prior to saving the post. When editing a post, the plugin converts it back into Markdown syntax.
The plugin also allows you to enable Markdown in comments and bbPress forums. In these instances the plugin adds a toolbar, and preview of the processed Markdown with <a href="http://code.google.com/p/google-code-prettify/" rel="nofollow ugc">Prettify</a> syntax highlighter applied (similiar to that used in the Stack Exchange websites such as <a href="http://wordpress.stackexchange.com/" rel="nofollow ugc">WordPress Stack Exchange</a>).
WP-Markdown stores the processed HTML, so deactivating the plugin will not affect your posts, comments or bbPress forums.

WP-Markdown

Version 1.5.1 of the plugin works almost perfectly.
I'm just waiting for the upcoming 1.6 update (which is in alpha on GitHub) to be pushed, so I can use GitHub Flavor-style codeblocks specifying the exact language.



Waiting for 1.6

Allows Markdown to be enabled in posts, comments and bbPress forums.

Simple Markdown vs WP-Markdown