I don't know why anyone would write their IPs in octal, but fair point

You can use a ULA if you want to. That's essentially the IPv6 equivalent of a private IP.

Why though? Having the same IP for both internal and external solves a bunch of issues. For example, you don't need to use split horizon DNS any more (which is where a host name has a different IP on your internal network vs on the internet). You just need to ensure your firewalls are set up properly, which you should do anyways.

Never claimed it was, please quote me where I said as much

o.O

The only valid regex is (.+). Maybe add a separate country field (especially because some Americans wholeheartedly believe that the entire world should understand that "foobar, TX" means "foobar, Texas, United States") (don't get me started on states whose abbreviations are also ISO country codes).

Unfortunately I guess business people only care about getting fewer support calls for missing shipping details, not correctness or a couple of calls from customers who live in the boonies. Then the proper answer is a form with a bunch of fields... which Americans will inevitably fuck up by making the "State" field mandatory despite most countries not having an equivalent.

What I'd really do is use one of those services that automatically fill on the address using google maps or whatever. Not perfect, probably not free, but a whole lot less work for presumably way fewer PEBCAKs from customers.