Editorially - a simple web-based collaborative Markdown editor, now open

This is nice looking, and I like the inline conversion of Markdown to visualized content. However, NSA.

What I mean by that is I don't want yet another third-party web service hosting my documents. I'd love this if it were something I could download and install in my network in the same manner as Etherpad Lite [1].

I'd even pay for it if I could install it in my environment because it looks slightly more glamorous than Etherpad.

[1] http://etherpad.org/

I'd pay for this and use it daily if it had inline comments, a la google docs. I've wanted a very long time Google Docs but in markdown. I want to collaboratively build a document but be able to comment (as metadata, not as text in the document itself) on certain paragraphs, bullet points, sentences, etc and have a discussion around those comments.