I heard from another user on Slashdot that Cox had enabled IPv6 for most of its residential customers. After upgrading my router firmware and rebooting it, and then renewing the DHCP lease on my computer, it looks like I now have IPv6 working at home.
I then tried pinging the hash website. At first, DNS lookup failed. Log into the DNS provider, create an AAAA record, renew the DHCP lease again…ping6 www.lasvegashhh.com now works. It also works for our new Red Dress Run site at rdr.lasvegashhh.com.