I am not sure that this is meant to be a "discussion forum". Of course we have to evaluate how we will want to use this platform first by gaining some experience, but I would rather recommend that proposals cannot be a set of "questions to be discussed" but should be a concrete proposal that needs legitimation. We have "enough" discussion platforms already, and this should not be "just one more platform for discussing".
But for us to know how to use the features we need of course first to experiment with them and learn the terms and "how-to" work with them.
So a "draft" like Robert's "Leadership" Document would be a candidate for a "proposal" which for a consensus could be put up for legitimation through this platform (instead of collecting "+1" through the mailing lists.
I would think of this platform as a "Gerrit for non code-related decisions".