I really would like IPv6 nameserver glue for my .com domains too. http://www.sixxs.net/faq/dns/?faq=ipv6glue
currently still lists Dynadot as a registrar unable to provide IPv6 glue for domains.
For this to be properly enabled, Register a domain name server
should take both an IPv4 and an IPv6 address for a single nameserver entry (e.g. ns1.example.com), for the domains that you can provide IPv6 glue for. (e.g. .com, .net, .org)