I find the discussion about whether or not NAT is a security feature or not interesting. To my mind NAT was intended to make ipv4 last longer in a clever way as address space dried up. A happy accident of this solution is a basic security feature.

Ipv6 doesn't (currently, will it ever?) have the same address space problem so each device anywhere could be globally routable. But we know that's not really a good thing security-wise. But why couldn't we implement NAT for it as a security mechanism, instead of an address space solution?

Admittedly I'm not expert so I might be talking shit.