Creates invalid HTML with preformatted blocks.

Markdown allows to use inline HTML. Hovever, when inputting a paragraph enclosed in <pre> tags, the markdown filter additionally encloses it in <p> tags, which is not valid HTML code. The test environments at daringfireball as well as at php-markdown implement this behaviour correctly, however, the markdown module adds invalid (in html terms) <p> tags.

An example:
The markdown code:

A paragraph.

<pre>
Prefomatted
multi-line text
</pre>

should be translated to:

<p>A paragraph.</p>

<pre>
Prefomatted
multi-line text
</pre>

but with the markdown module (without any other activated input filter) it becomes:

<p>A paragraph.</p>

<p><pre>
Prefomatted
multi-line text
</pre></p>

which is invalid HTML.