OSPFv3 Neighbors do not need to be on same subnet

Check it out:

R2 F0/0 <-----> F0/0 R3

Here is R2's config:

R2#sho run int f0/0
Building configuration...

Current configuration : 153 bytes
!
interface FastEthernet0/0
 no ip address
 duplex auto
 speed auto
 ipv6 address 2001:2::2/64
 ipv6 address FE80::2 link-local
 ipv6 ospf 1 area 0
end

Here is R3's config:

R3#sho run int f0/0
Building configuration...

Current configuration : 153 bytes
!
interface FastEthernet0/0
 no ip address
 duplex auto
 speed auto
 ipv6 address 2001:3::3/64
 ipv6 address FE80::3 link-local
 ipv6 ospf 1 area 0
end

R2's show commands:

R2#sho ipv6 ospf ne   

Neighbor ID     Pri   State           Dead Time   Interface ID    Interface
3.3.3.3           1   FULL/DR         00:00:35    4               FastEthernet0/0

R2#sho ipv6 route  
IPv6 Routing Table - 5 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
       U - Per-user Static route
       I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
       O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
C   2001:2::/64 [0/0]
     via ::, FastEthernet0/0
L   2001:2::2/128 [0/0]
     via ::, FastEthernet0/0
O   2001:3::/64 [110/10]
     via ::, FastEthernet0/0
L   FE80::/10 [0/0]
     via ::, Null0
L   FF00::/8 [0/0]
     via ::, Null0

R2 can now ping 2001:3::3

R2#ping 2001:3::3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:3::3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/20/56 ms
R2#

This is possible because neighbors are known by their router-ids and link-local addresses are used as next hops, not the actual interface addresses.