How to Allow Markdown in Comment without Plugin

Comment form in WordPress is... adequate. It does its job but has a lot of room for improvement. And our first step is implementing better formatting like Markdown.

Comment form in WordPress is… adequate. It does its job but leaves a lot of room for improvement. And our first improvement is implementing better formatting like Markdown.

Markdown is a syntax for simple formatting. For example **this text** becomes bold and *this one* becomes italic.

Let’s implement it:

Step 1: Check if your theme uses comment_text()

Open comments.php in your theme and check how does it outputs the comment content. Does it uses comment_text()?

Yes? Proceed to next step.

No? Then you need to wrap the code like shown below:

...

// If original code is like this:
echo $comment->comment_content

// Wrap it like this:
echo apply_filters( 'comment_text', $comment->comment_content );

Step 2: Add Markdown parser

Hook into comment_text and apply the Markdown while removing the other filters.

add_action( 'wp', 'comment_md_init', 9999 ); 

function comment_md_init() {
  global $post;

  // abort if in blog page or no comment yet
  if( is_home() || $post->comment_count <= 0 ) { return; }

  require_once 'parsedown.php'; // download the file below

  // Remove escaping some symbols
  remove_filter( 'comment_text', 'wptexturize', 10 );

  // Remove auto anchor link
  remove_filter( 'comment_text', 'make_clickable', 9 );

  // Remove auto <p> tag
  remove_filter( 'comment_text', 'wpautop', 30 );

  // Markdown formatting
  add_filter( 'comment_text', 'comment_md_format' );
}

// Format the markdown
function comment_md_format( $text ) {
  $pd = new \Parsedown();
  return $pd->text( $text );
}

Step 3: Try it Out

Here’s a Markdown Cheatsheet. Go try some in your comment form.

Writing comment with Markdown syntax
When posted, the Markdown comment is successfully parsed

Done! You might need to change the CSS to make it looks better.

Doesn’t Work or Formatting Messy?

Check if there’s another filter that overrides your parser. At the bottom of your comment_md_init function, add this snippet:

// at the bottom of comment_md_init() function
global $wp_filter;
var_dump( $wp_filter['comment_text'] );

Refresh your page and see the order of filters. Remove the one that you think is the problem and try again.


Step 4 (Optional): Let the visitors know that it supports Markdown

Below are two recommended ways to do it, pick one:

OPTION A – Simple Text

This is as simple as it gets. Feel free to change the text.

add_filter( 'comment_form_defaults', 'comment_md_add_guide' );

function comment_md_add_guide( $defaults ) {
  $icon = '<svg width="20px" height="15px" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 640 512">
  <path d="M593.8 59.1H46.2C20.7 59.1 0 79.8 0 105.2v301.5c0 25.5 20.7 46.2 46.2 46.2h547.7c25.5 0 46.2-20.7 46.1-46.1V105.2c0-25.4-20.7-46.1-46.2-46.1zM338.5 360.6H277v-120l-61.5 76.9-61.5-76.9v120H92.3V151.4h61.5l61.5 76.9 61.5-76.9h61.5v209.2zm135.3 3.1L381.5 256H443V151.4h61.5V256H566z"/>
  </svg>';

  $text = 'This form supports markdown. <a href="https://commonmark.org/help/" target"_blank">Read guide »</a>';

  $guide = "<p class='comment-md-guide'> $icon <span> $text </span> </p>";

  $defaults['comment_notes_after'] .= $guide;
  return $defaults;
}

OPTION B – Editor Toolbar

The snippet below will apply hEditor to the comment form. It’s a very lightweight script and the same one used by our comment form.

add_action( 'wp_enqueue_scripts', 'comment_md_enqueue_toolbar', 9999 );

function comment_md_enqueue_toolbar() {
  global $post;

  // If comment is open
  if( isset( $post->comment_status ) && $post->comment_status == 'open' ) {
    wp_enqueue_style( 'h-editor', 'https://hrsetyono.github.io/cdn/h-editor.css', [] );
    wp_enqueue_script( 'h-editor', 'https://hrsetyono.github.io/cdn/h-editor-wp.js', [], null, true );

    wp_localize_script( 'h-editor', 'localizeEditor', [
      'textareaSelector' => '#comment',
      'buttons' => [ 'bold', 'italic', 'link', '|', 'bullist', 'numlist', 'quote', '|', 'undo' ],
      // Other buttons:
      // h1, h2, h3, image, code, pre, hr, strike, redo
    ] );
  }
}

Conclusion

I hope Markdown can be natively supported for Comment. But for now, we can use this tutorial which doesn’t leave any noticeable footprint. Especially if you pick Option A in Step 4.

Also do not be afraid of implementing this on a non-techie website. Even if they don’t use any Markdown, it still functions like the old comment form.

Let me know if you have trouble or suggestion in the comment below 🙂

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Henner Setyono
A web developer who mainly build custom theme for WordPress since 2013. Young enough to never had to deal with using Table as layout.

2 Comments

  1. As I has read all the code but I have one problem I don’t have WordPress Programming knowledge so, can you please suggest me the Plugin or share the post if you have any already posted. Thank you.

    • Hi Shazaib, Unfortunately there's no plugin for the above code.

      If you have knowledge in other programming language, WP isn't that hard. It's still PHP at the end of day