[andrewaylett]

You've been downvoted because this shouldn't be true, but since no-one else has stepped up, I'll bite :).

It's perfectly possible to do IP-based rate-limiting in the IPv6 world, you just need to do it based on different prefixes, rather than full IPs.

As a specific example, my ISP -- as is quite usual -- hands out /48s. So in the same way that you can rate limit my entire NAT'd IPv4 connection with a single entry, you can rate limit my entire IPv6 connection with a single entry, by storing the prefix.