It just seems obvious to me that collaborative fiction writing is facilitated by co-authors who work together to make plans for their collaboratively written story. Take a look at some collaboratively written science fiction novels that were listed by Alex Carnevale and see what he had to say about the nature of the writing collaborations behind those novels.
Here at this wiki website there have been several proposals for collaboration that included the idea of co-authors NOT talking to each other. Wiki fiction stew has this rule: "contribute a new original character without having to consider story details". Of course, with such a rule it was not easy for anyone to understand how to integrate all of the characters into a coherent story. Eventually, questions were asked about characters and no answers were provided. The project stalled.
One-paragraph-at-a-time has this rule: "don't discuss the plot with other authors anywhere". In contrast, the successful collaborations I have been involved with such as VirileMail and The Search for Kalid were facilitated by large amount of communication between collaborating authors. Meta pages and online chat are particularly effective for developing collaboratively written stories. I believe that this wiki website needs to continue to develop existing and new tools that will support collaborative fiction writing.
The rules for One-paragraph-at-a-time also say that "once the story has gone past the initial stage" then it is alright for co-authors to discuss the plot. I'm not you is being created according to the rules for "One-paragraph-at-a-time". I'm not you was started a year ago. JWSchmidt, Davinci, Serprex, Micmac99 and Modred have contributed paragraphs to the story. I'm going to assume that I'm not you is past "the initial stage".
I'm not you is about a woman (Sara) who has an internal "visitor", a mysterious inner voice that is trying to communicate with her...or through her. I propose that I'm not you be written as a science fiction story, but it is also a kind of mystery. Sara does not know what is happening to her, how it is possible for a second consciousness to share her brain. The reader will follow along with Sara while she discovers what is going on.
As a science fiction story, there is nothing magical or supernatural about the means by which Sara shares her brain with another mind. I propose that I'm not you is a story of first contact. What kind of alien being would make itself known to humans in the odd way depicted in I'm not you? Could such contacts have been occurring to other humans through all of human history, but only now, in our technological age, do we finally have the means to understand what is happening to Sara?
related reading: Synthetic Biology - questions about artificial lifeforms that might visit Earth.