For example, when this code is interpreted as Markdown:
<p>This is a test</p>
<p>This is a test</p>
It produces the following result (quoted for exposition). In Markdown, the 4 spaces before the second <P>
create a code-block. Markdown isn’t a pure super-set of HTML, so you will sometimes get unexpected results when copy-n-pasting HTML into Markdown:
This is a test
<p>This is a test</p>
The Markdown generated HTML is:
<p>This is a test</p>
<pre><code><p>This is a test</p></code><pre>