__ssh_authorized_keys resets owner and permissions of the ~/.ssh/authorized_keys file when removing an existing/updated entry

so you end up with e.g.
\# ls -lh ~rails/.ssh/authorized_keys
-rw------- 1 root root 6.1K Sep 27 14:46 /home/rails/.ssh/authorized_keys

instead of
\# ls -lh ~rails/.ssh/authorized_keys
-rw------- 1 rails rails-group 6.1K Sep 27 14:46 /home/rails/.ssh/authorized_keys