I literally had to interrogate an LLM to explain what this was about, because to me, indeed, when I see 169.254 I think "Ah, someone unplugged something critical and the network is now completely down." I didn't even know that in ipv6 land there are any reasons to use link-local addresses for anything. I mean, there still basically isn't a reason for 99.99% of people, I think. But it's interesting.

I also didn't realize that part of the idea behind these LL things was one of the rounds of wishful networking ideas of the 90s or 2000s, kind of a cousin of UPnP and mDNS in that way (in increasing order of eventual usefulness).

Considered completely in a vacuum, especially ignoring the WAN, I can see how it seemed silly that if you plugged three computers and a printer into a switch, rolling random IP addresses like this could have allowed things to be discoverable and to function locally (I thought mDNS or "Bonjour"/"Rendezvous" as Apple called it came much later, but I know my PCs could "see" each other with NetBIOS or whatever long before mDNS was invented).