The Official Feed Viewer Blog
We have decided to remove the necessity to login with Microsoft account. In the past, it was a good reason because it allowed users to use the same identity on multiple devices. It worked well until Microsoft introduced on screen software buttons. The Microsoft account login dialog was never adapted to software buttons and did not work well. The second reason why we are abandoning Microsoft account is its unreliability dated on March 7. The third reason comes from fact that vast majority of users does not trust Microsoft that signing in with Microsoft account in third party application is safe for them. Microsoft does not communicate well enough that app receives only an anonymous identification unique to the user.
Today Feed Viewer has its own identity management system which guarantees users anonymity and allows them keep their content synchronized among multiple devices. It is as simple as possible without decrease of security level. Feed Viewer identity is no longer tied to Microsoft account. Remember that you must send your identity to the new device before uninstalling the app from the previous one.