Hi team,
If multiple ospfv3 areas are configured, I would imagine that you can use the link local addresses for the neighbour discovery and for passing route information within the specific area.
However, when multiple areas are used including transit areas (for areas not directly connected to area 0) the use of Global Unicast addresses would be needed?
I created a topology with a virtual link going through a transit area and my remote area (not connected to backbone) received the prefix from area 0 via OSPFv3, however, it couldn’t not ping the prefix and I was only using link local addresses at the time. Once I created IPV6 addresses between the routers, the ping then worked.
If you could assist with this that would be great! 
Thanks,
Andrew