Comcast has a decent ipv6 technology group (by necessity - they were an early adopter/innovator of carrier-grade v6 as they have more CPE to address than can be fit into 10/8). If you ever become interested in resolving this you may want to dig through http://www.comcast6.net and see if you can find a direct contact to work with.

I don't have any contacts myself, I'm just a customer and interested observer.