The point was whether 128 bit addresses are actually required - someone was claiming that 64 bit addresses would have also been exhausted, and I pointed out that the current strategy for handing out IPv6 is anyway using up the address space at a similar pace to the situation where we had a 64 bit address and were handing out /64 addresses to individual consumers. There were even some comments claiming certain ISPs are handing out /56 spaces to end consumers.

Ethernet MACs have 48-bit addresses, and I don't think we've run out of those, and I also don't think is anyone is even worrying about running out of those, so 64-bit IP addresses probably would have been sufficient.

But given all the drama with IPv6, I think it was reasonable to go with 128-bit addresses just so we don't have to go through all of this again.

On a related note, messing up the assignment of IPv6 address was actually accounted for. If you look at any unicast address that's currently live, you'll see that it begins with a "2". This is because addresses are only being assigned from 2000::/3:

* https://www.iana.org/assignments/ipv6-address-space/ipv6-add...

If, for some reason, we realize there's a mistake in how things were done with that space, it will be declared legacy/deprecated, and IANA will start over with addresses from 4000::/3. If that is screwed up, then 6000::/3 will be next, then 8000::/3, a000::/3, and finally c000::/3.

So the Internet community has six tries to get IPv6 addressing correct.