So I was writing that long post yesterday and got annoyed with having to write HTML. Having rewritten an upcoming pronet article in Markdown, I've grown to like it, and wanted to have the same ability to write in Markdown here as I do in MT.
So I fixed it with Greasemonkey. I used some CGI scripts to do the actual conversion, accessible with GM_xmlhttpRequest. Far from the ideal of native support, but it's serviceable. Hopefully I'll find the patience to package and publish it.
Except of course that no one cares.