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.

edik

Some WordPress functions outputs character entity references. The most of these are not allowed in XHTML. So if your WordPress installation uses the mime type ‘application/xhtml+xml’, the generated sites could have invalid xhtml code and the browser would display the syntax error page.
Convertentity converts all entity references into their corresponding characters with the exception of the references for the following characters: ‘<>&”
Theses references are the only ones which are allowed in XHTML.

Convertentity

Converts all character entity references, which are forbidden in XHTML, into their corresponding characters.

Escape HTML vs Convertentity