Comment by oarsinsync

Amusingly, there a lot more special IPv4 networks that you just don't know about too. e.g. Link local IPv4 is 169.254.0.0/16. It just isn't auto-configured on every IPv4 interface by default, like fe80::/10 is on IPv6 interfaces, and the TCP/IP stacks on most platforms do not enforce the link-local properties of it in IPv4 like they do in IPv6.

It's like the difference between HTML and a strictly typed language. Permissiveness and flexibility is both a blessing and a curse. As with a lot of things, which thing it is in any given situation depends greatly on the situation.