From the post:
Today we are making it easier to review and collaborate on prose documents. Commits and pull requests including prose files now feature source and rendered views.
Given the success of GitHub with managing code collaboration, this expansion into prose collaboration is a welcome one.
I like the “rendered” feature. Imagine a topic map that show the impact of a proposed topic on the underlying map, prior to submission.
That could have some interesting possibilities for interactive proofing while authoring.