Earlier today I tried to bring up a node with Ipv6 IP. heat.myAddress=2a00:8[...] and that seemed to sync ok.
I queried the hallmark and copied it to conf, to end up with:
2017-01-30 13:47:53 INFO: Your hallmark is invalid: 88db63d75518a[...]522 for your address: 2a00:878[...]
Fatal error: java.lang.ExceptionInInitializerError
2017-01-30 13:47:53 INFO: Shutting down HEAT server 0.9.2
Definitely this is not urgent as Ipv6 has been coming two decades
But just for your info.