Unbound AAAA filtering
If you have ever tried to announce an IPv6 prefix into a network without access to the global unicast subnet you will notice many things break as applications assume otherwise. For me this is a problem when announcing a Yggdrasil prefix (200::/7).
Advertising a Yggdrasil prefix
The solution that I've found is to prevent applications from resolving IPv6 addresses by filtering global unicast AAAA records using Unbound.