darrinb

Easily include raw markup languages (HTML, CSS, PHP, etc.) in comments using custom quicktags. No need to encode, the filter does it for you. Creates convenient “encode” buttons for comment authors in the HTML editor.
Also adds basic quicktag buttons on the comment forms, using the Quicktag API built into WordPress (as of 3.3).

WP Comment Encode

Satya Prakash

To show <code>text</code> to visitors we need to enter <code>&lt;b&gt;text&lt;/b&gt;</code> in our WordPress Text editor. For posting code online, three characters (<code><</code>, <code>></code> and <code>&</code>) need to be escaped. We can do that online <a href="http://www.satya-weblog.com/tools/htmlencode.php" rel="nofollow ugc">tool</a>, manually converting <code><</code> to < etc. or using easy to use Plugin. It also helps with syntax Highlighter where you need to escape markup before putting that code in WordPress Editor.
It escapes markup code inside <code><pre></code>, <code><code></code> and <code><tt></code>. 
The plugin can also be used with any Syntax Highlighter where you need to escapes Markup inside <code><pre></code>, <code><code></code> and <code><tt></code>. Just put your code inside Text Mode of Editor and then either Save as Draft or Publish. Check you code now and it may have converted for online posting of code.
This plugin only come into effect when we save a post and it only affect those text written inside <code>&lt;pre&gt;</code>, <code>&lt;code&gt;</code> and <code>&lt;tt&gt;</code> tag.
For more information about this plugin and wordpress setting related to this plugin, please <a href="http://www.satya-weblog.com/" rel="nofollow ugc">check here</a>.
Related Plugin – <a href="https://wordpress.org/plugins/escape-html-for-prism-syntax-highlighter/" rel="ugc">Escaping Markup for Prism</a>
Another WP plugin from <a href="http://www.satya-weblog.com/" rel="nofollow ugc">Satya</a> – <a href="https://wordpress.org/extend/plugins/performance-optimization-order-styles-and-javascript/" rel="ugc">Performance Optimization: Order Styles and JavaScript</a>.

Escape HTML

This plugin Escape Markup Code (HTML, etc) to Post Code Online.

WP Comment Encode vs Escape HTML