A site can be owned, or not. If it is owned we ask two simple questions "Who Are You?" and "Are You The Site Owner?". The separation of these two questions is important, as we will see.
Federated Wiki is only concerned with "Who Are You?", authentication, when the site is owned and you are performing an action that only the site's owner is allowed to perform.
To make different authentication schemes easier to develop, and deploy, there is an aspiration to move towards modular authentication. For those situations where solutions are already via a reverse proxy it will be possible to pass the user's identity into the server.
For those wanting to secure private wiki farms we anticipate that user authentication, and read authorization will be performed by a reverse proxy.