The markdown code supposedly lives at the pagedown project on code.google.com.
You may also find these files to be useful:
Personally, I find it easier to just use normal
<textarea> processing followed by a call to
StackExchange.MarkdownEditor.refreshAllPreviews(). You can see that in action in this handy userscript.
StackExchange.MarkdownEditor has these tempting functions (¿not particularly documented?):
Tangential PS: To help with related searches...
WMD stands for Wysiwym MarkDown.
From wmd-editor.com (archived):
So WMD is something new: a Wysiwym Markdown editor.
- Wysiwym stands for What You See Is What You Mean. WMD produces clean semantic HTML, leaving presentation details like fonts and colors up to style sheets. But you're not left in the dark about cosmetics; as you type, WMD's live preview shows you exactly what your text will look like after the current styles have been applied.