Storytella[0] takes the same approach. It uses a Markdown editor in a single pane, no preview, which is also based on CodeMirror[1]. CodeMirror makes this kind of editor straight forward to build, with a lot of configuration and extension options. This seems to hide a lot of the configuration, so I would think is great for dropping into new admin or comment systems where you need rich text but don't want to allow arbitrary HTML.
I would consider switching over to it, as it would mean less code for me to manage, but I'd need the CodeMirror extensibility exposed.
(disclosure, I built Storytella)