I (the guy two comments up) am in Canada through another provider. Whether the address range just isn't as well known and documented on whitelists, or one of my neighbors (IPv6 wise) runs botnets, there is no doubt that it is treated as much more suspicious traffic when I'm going through IPv6.

And this is well known in the industry. The IPv4 world has had enormous mapping and trust ratings and understanding -- coupled with a scarcity that gives range owners or operators a higher incentive to care about what happens on it -- while a lot of people are still completely in the dark about IPv6 and still treat it like some scary unknown.