Currently the /account/whoami endpoint does not mention anything about guests, which is a bit of an oversight. The implementation of the endpoint got created such that guest access was declined.
Guests are allowed to use /account/whoami. When a guest makes a request, the response will have
an added is_guest: true field - this field is optional (default false) otherwise.
None forseen. This corrects a mistake.
None relevant.
Guests will be able to know their user ID, as they would when they registered in the first place.
While this MSC is not in a stable version of the specification, implementations should use
org.matrix.msc3069.is_guest in place of is_guest. Callers should note that they might see
M_GUEST_ACCESS_FORBIDDEN errors if the server is not implementing this MSC.