Here is a demo:
https://www.youtube.com/watch?v=97lAMRrAcF4&feature=youtu.be
I have previously posted on reddit/r/vim here: https://www.reddit.com/r/vim/comments/a2kjx9/work_in_progress_rich_text_editing_with/
Do you think there is an audience?
Do you think that it needs to be collaborative and implement branching in itself, or it is better just as an editing interface for Markdown and let Git handle branching/merging in plain text?