Hey, great and informative post! I know it's been a while since it was published, but it is featured on the welcome page and maybe someone sees my comment and can help. 

I'm really new here (joined yesterday) and wanted to test the posting feature, using markdown.

I clicked on the top-right option until markdown was selected, but as soon as I typed anything in the post message body, "raw html" was selected. If I deleted whatever I typed in, "markdown" got selected once again. Was I doing something wrong? Thanks in advance!