> No, IPv6 as it is supposed to be implemented gives (say) a single server a /64, which is for all intents and purposes an inexhaustible supply of IPs. You could in principle have an IP per site you visit and have plenty left to spare.

No, as it's supposed to be implemented a single internet-routable /64 is used per *network* and then most devices are expected to assign themselves a single address within that network using SLAAC.

ISPs are then expected to provide each connected *site* with at least a /56 and in some cases a /48 so the site's admins can then split that apart in to /64s for whatever networks they may have running at the site. That said, I'm on AT&T fiber and I am allocated a /60 instead, which IMO is still plenty for a home internet connection because even the most insane homelab setups are rarely going to need more than 16 subnets.

> So if I wanted to annoy GitHub, I could connect to them without ever using the same IP twice. Their response would have to be banning my /64, or possibly /56.

Well yeah, but it's not like it's exactly rocket science to implement any sorts of IP rate limiting or blocking at the subnet level instead of individual IP. For those purposes you can basically assume that a v6 /64 is equivalent to a v4 /32. A /56 is more or less comparable to /25 through /29 block assignments from a normal ISP, and a /48 is comparable to a /24 as the smallest network that can be advertised in the global routing tables.

Its not harder to rate limit a /64 though.