Allow tags between shortcode in comments

You want to allow folks to post code in their comments, like on here were we can just do <p>something</p> without having to worry about doing any > or < stuff? I think you’ll still want those special html characters converted to their respective entities, but you need to stay under the radar to avoid getting the tags stripped out by wp_filter_kses.

You’ll need to hook into a filter called pre_comment_content and convert anything within your shortcode tags to their HTML entity equivalents.

<?php
add_filter('pre_comment_text', 'wpse29367_pre_comment_text', 9 );
function wpse29367_pre_comment_text( $text )
{
    $text = preg_replace_callback( 
        '/(\[html\])(.*?)(\[\/html\])/i', 
        create_function( '$matches', 'return $matches[1] . htmlspecialchars( $matches[2] ) . $matches[3];' ),
        $text
    );
    return $text;
}

Then you can decode them or whatever in the shortcode function you create:

<?php
add_action( 'init', 'wpse29367_add_shortcode' );
function wpse29367_add_shortcode()
{
    add_shortcode( 'html', 'wpse29367_shortcode_cb' );
}

function wpse29367_shortcode_cb( $atts, $content = NULL )
{
    /**
     * decode html entities here if you want
     * eg: 
     * return htmlspecialchars_decode( $content );
     */
}

The final piece of the puzzle, adding the do_shortcode filter to comment_text.

<?php
add_filter( 'comment_text', 'do_shortcode' );

You could make this work very well for your visitors by using a plugin like SyntaxHighlighter Evolved, and just using the first bit of code I posted along with adding the do_shortcode filter to comment_text.

Note: didn’t test any of the above. Copy and paste with caution.