Are numbered headings in Markdown / Rdiscount possible?

I'm trying to produce html with section / subsection headings resembling the following:

1. My top-level topic
   1.1 My first subtopic
   1.2 Another subtopic
         1.2.1 A sub-subtopic
2. Another top-level topic

Are there any implementations of Markdown capable of producing these kinds of numbered section headings?

Yes, try Pandoc. This works for me:

pandoc --number-sections < test.md > out.html

(Source)

Markdown to produce the numbered outline you mention in the original post looks like this:

# My top-level topic

## My first subtopic

## Another subtopic

### A sub-subtopic

## Another top-level topic

If you want deeper indenting for sub-sections, you might be able to achieve this with inline CSS. For example, placing this at the top of the above Markdown source indents the headers:

<style type="text/css">
  h2 { margin-left: 10px; }
  h3 { margin-left: 20px; }
</style>

But say you had paragraphs of text under your headings... I don't know how to indent that to the same level as the above header.

Update 2015-10-18: Markdeep has numbered headings (and many other fancy features). Check that out too!