I have found an issue in this question: https://stackoverflow.com/questions/491566/how-to-get-list-of-values-in-group-by-clause

Check this out. I enter the following piece of HTML:

    <code><pre>hello</pre></code>

It is rendered as such:

<code><pre>hello</pre></code>

When I check the rendered HTML in my browser, what I get is this:

    <p><code></code></p>
    <pre><code>hello</code></pre>

So some extra `<code/>` element and paragraph are rendered.