I have had my iPv6 working for quite some time and it's still currently working but I never noticed until now that when I first had setup my iPv6 in my AirPort Extreme, I had entered the dynamic global hostname of my tunnel in the use dynamic global hostname section in my Extreme but I left it unchecked. Now after seeing this unchecked, does it need to be checked? I can't remember if it needs to be checked or the dynamic global hostname isn't needed.
That setting is used for Wide-Area Bonjour. Unless you have dynamic DNS setup with a provider using TSIG based updates, and the Bonjour services exported by the Airport, then it doesn't do anything.
I looked into exactly what this does, and while it seems potentially useful, all it exports are the various SRV records. No A/AAAA or friends.