I seem to recall hearing somewhere on HN that some ISPs even turn CGNAT on for IPv6 connections (in fact, I'm pretty sure AT&T's LTE has it). I have no idea why

I seem to recall hearing somewhere on HN that some ISPs even turn CGNAT on for IPv6 connections (in fact, I'm pretty sure AT&T's LTE has it). I have no idea why, other than people being so used to packets not routing to their local box that they've disabled their firewalls. The people who made that decision probably went to the same school that told network admins to disable IPv6 on VPN connections.