Whilst I do enjoy the idea that is a Markdown editor, I think one of the main feature missing from this and most(?) is the ability to continue bullets and code indentations. Shameless plug I know, but that is why I built and use the following when editing Markdown in a textarea:
Good work, like it a lot. I almost feel allowing tabs should be a browser based setting, I'd have it enabled, but I can imagine other people wouldn't never need to use a tab.
https://github.com/jamiebicknell/Markdown-Helper