I was disappointed to see that so poor documentation exists on how to enable IPv6 on a RaspberryPi running Pidora (the Fedora version for the RPi).
After hanging here and out, I finally simply managed to run it using NetworkManager configuration.
Since my RPi is a headless (no display machine), I simply installed XQuartz on my Mac laptop and enabled X11 Forwarding on my SSH session.
By default, the sshd server on RPi does not enable it, so you have to add the following lines to /etc/ssh/sshd_config:
X11Forwarding yes X11UseLocalhost no
Then restart the service:
# service sshd restart
And on your laptop connect by ssh with the following options:
ssh -Y firstname.lastname@example.org
Then launch nm-connection-editor and edit eth0 network connection and go to IPv6 tab. Simply select the configuration to Automatic instead of Ignore which is default.