Hi,

All open differential submissions require authentication even if they are marked as Public. Once the submission is marked as close, non authenticated users can access to it, but not always.

1. Open submission with Public access not readable by guest: https://phab.enlightenment.org/D4154
2. Closed submission with Public access readable by guest: https://phab.enlightenment.org/D4000
3. Closed submission with Public access not readable by guest: https://phab.enlightenment.org/D4307

We are using:

1. phabricator 9da15fd7ab7071e3b7361463229abd4e918d9d94 (Jul 10 2016)
2. arcanist f1c45a3323ae20eefe29c0a22c7923fe8b151bbf (Jul 2 2016)
3. phutil 5fd2cf9d5ddd38424a54a8fba02398d527639970 (Jul 9 2016)

Cheers,