&gt; No, not everyone runs behind a NAT system. Ever been to a university where everyone gets an non-RFC1918 IPv4 address? That&#x27;s how IPv6 is. When I worked at Microsoft, everyone had a routed address on their workstations, too.<p>Every normal customer is, every normal business is.  Old institutions do not count because they are in a privileged position nobody else on the web is.<p>&gt; As you just admitted, NAT breaks things.<p>And we learned to deal with it for many, many years.  For many of us, a NAT is considered a feature not a bug in fact.<p>When I run a server I already have to assume that clients are NATed and as such I design my system to work that way.  IPV6 only is a non existing part of the internet and as such not really something to optimize for.  I get absolutely nothing currently by enabling IPV6 on my server because I cannot depend on it.