There is some additional info in the about page:
And in this doc: http://docs.xstatic.site/markdown_db86ac26-f232-4400-a544-d5...
updating a document in S3 is bad idea... that said the tech is interesting.
Started editing in one. Changes did not appear in the other.
Pressed Ctrl+S in both windows, and it seems the last one wins. So basically the first one loses their work.
But probably when S3 is busy, you can edit, refresh and not see your changes.