[akdev1l]

> So when you need to figure out if a device is in the same building as you, is it easier to say "1.2.3. - oh, that's my building" or "1234:5678:90ab:cdef:1234:5678:90ab:: - oh, that's my building"?

This is a very poor straw man.

In IPv6 world you wouldn’t use all the significant digits randomly and because you have so many you could actually use one of the octets to perfectly encode the building information:

Building 1: 2001:1:: Building 2: 2001:2::

(You can go further with this concept and encode region/country/state/etc into the addressing as required)

[Control8894]

This is a very poor straw man.

In IPv6 world you wouldn't get 2001::/112, you'd get 2001:1234:5678:90ab::/48. So your building might actually be at best something like 2001:1234:5678:90ab:1::.

[p_l]

That's for globally routable addresses, which you wouldn't get as nicely allocated in v4 either, if at all.

For equivalent of 10./8 space, you'd have ULA, which can be subdivided this way just fine (and arguably since fc00::/8 is left in limbo, you can use that. Or just decide to fit whatever addressing scheme you decide into 80 bits left after typical fd00::<48bit random>/48.

So sorry, your v4 strawman isn't too good either.