This is so that observers being registered can refer
"sub-observers" recursively. When such observer is deleted,
the whole underlying subtree is removed with it. This facilitates
the process of unregistering observers - ie: when the main
observer goes down because it is destroyed, all of its sub-observers
are removed as well, because in this architecture they are expected
to be aggregated to the main observer.
Temporary Platform objects were registering themselves.
The move ctor would then initialize the final object in
the circular buffer (see PlatformSystem), but it would
leave the address of the temporary object registered in
the ObserversManager.
