Hmm, I missed this before. Is this always the case? Because it is only the case some of the time in PHP Markdown Extra - which this should be emulating. For example, in PHP’s implementation a heading (h1-6) before the raw HTML block does require a blank line, while a paragraph does. I realize that the difference in the implementation has some effect on these edge cases, but I try to go with what feels less buggy. So, for example, if the document author leaves out the blank line after a paragraph, that feels more like a bug- unless, of course, the docs specifically say otherwise. Unfortunately, PHP’s docs make no mention of this requirement.

So my question to you is, did you change the behavior, or has Python-markdown always had this behavior? If this has previously Been the case, then let's leave it for now, but if not, then I'm inclined to consider this a regression and back out the changes.