Short Version: Why when I impersonate a web-request made by Windows Store app, I get WindowsIdentity object with correct user name, but its IsAuthenticated prop
I think I've stumbled across the same (Calling a WCF service using Windows Auth from a Windows Store App) and it looks like Windows Store Apps with enterprise authentication prevent calls to services on localhost using impersonation.
When I hosted my service on another server on the domain it worked just fine.