Comcast is the reason I disabled IPv6. They'd frequently route traffic over IPv6 to... Nowhere. Websites of major tech companies such as Google and GitHub would occasionally get routed wrong and just... Hang. It's like they black holed outbound IPv6 traffic. The traceroute6 output would quit displaying new routes.
Never had that problem on IPv4. So I ended up disabling it.
(I do have an unrelated issue that sometimes they can't route traffic between two customers in the same general area. Traffic tends to go out to the west coast Comcast DCs and get stuck, never comes back. We're midwest).
Github is IPv4-only to this day. So you should not be getting AAAA records for it, nor any v6 routing issues to a v4 address.
(Also, my experience with IPv6 on Comcast was relatively solid; just hated their billing department. Now my ISP doesn't offer IPv6 at all, which isn't great.)
Used to run the network for a large hosting company. Can confirm, I disabled all peering and transit on one set of border routers for maintenance, restored, and then did the same on the other set.
In both cases, I disabled everything, and then only restored IPv4. Took me a week to notice and restore IPv6. Not a single support request was received relating to the week long IPv6 outage.
This was when I gave up and removed IPv6 from my home network. I’m now behind IPv4 CGN, and don’t care. It works.
Never had that problem on IPv4. So I ended up disabling it.
(I do have an unrelated issue that sometimes they can't route traffic between two customers in the same general area. Traffic tends to go out to the west coast Comcast DCs and get stuck, never comes back. We're midwest).