Microsoft Azure’s use of non-US IPv4 address space in US regions

Which all has exactly zero to do with what is meant here by "non-US IPv4 address space", as it in no way implies that the systems that you assign those addresses to are themselves located in those geographic areas, let alone that their users speak a particular language and similar crap that people have overloaded the meaning of IP addresses with. It's a division for administrative purposes, nothing more, and as you might notice, it doesn't even have country granularity.

(Also, the question was rhetorical - I know how that idiocy happened, and I expect that most people here do.)

Exactly. It's the fact that many sites rely on GeoIP databases to try to offer the best localized services to people coming from various regions. GeoIP databases can also be used by firewalls, of course, to block all connections coming from a certain region.

Yeah - but what's the point of GeoIP databases? Most if not all of the use cases are idiotic. The browser tells me that the user understands English and French, but since the GeoIP database tells me the client's address is "brazilian", I'll deliver portuguese text! WTF? Similarly, routing requests to servers in the same country is kinda stupid - you want to achieve responsiveness, and responsiveness comes from shortest paths in the network graph, not from being inside the borders of the same country, or even from shortest geographic distance. In that case some suboptimal routing at least should be of little consequence, so it might be a usable approximation. Limiting access to content because you are in the wrong place is about as counter to the idea of the internet as you can get, so it's idiotic simply because of that. There simply is no sane reason to even have a concept of a "location of an IP address", other than its location in the network graph for packet routing purposes.

(edit: and the first one of those is causing lots of unnecessary pain, not only to travellers who suddenly have to deal with a "different internet" simply because they moved their body to a different place on the planet, but also for people in multi-lingual countries, who regularly have to deal with moronic websites forcing them into some particular language version that supposedly is the "language of their location", ignoring the fact that the user not only doesn't understand the language, but specifically tells the server via appropriate headers which languages the user understands.)

They will have to proxy stuff sure. But they need to start to roll out ipv6.

Many cloud customers would be fine with IPv6-only VMs and one IPv4 adddress on the outside of their load balancer. Yet cloud providers are building the opposite architecture.

They need to start with a dual stack, that works for over 97% of the internet. Then v6 would be of actual use for customers and ISPs would have more reason to support v6.

And a lot of IP stacks will treat any traffic from it as invalid. Even if the standards were revised to declare it as usable, it'd be impossible to use in practical terms.