They tend to get moderated away most of the time, which you can help by flagging them or emailing them to hn@ycombinator.com. Supercilious PSAs don't do any of that.
It's very common on HN. I do it too. Mostly because we spend a lot of effort avoiding these platforms, and when something bad happens to a person because of it, we can shout, "Ha! My paranoia is justified!"
If you're working day to day as an engineer, you end up mostly thinking in unhappy cases and 99.99% uptime scenarios, so it actually seems like helpful advice.
Far from it. Archive.org is a passion project funded and run by a moderately wealthy guy (Brewster Kahle). Or at least, he had a few millions when he started it, and I'm certain the org has been a money pit for him. Hopefully some kind of foundation exists to keep it going after he passes, but it's not a certainty.
It's inevitable that they go dark. They piss off too many people regarding IP rights, and people hate to have proof out in the wild of what they said or did in the past. Plus a ton of other reasons; more people have an interest in it disappearing than have an interest in it surviving.
I mean, when it dies it will be a greater tragedy than the burning of the library of Alexandria (at least many of the books there were copied elsewhere), it will be a tremendous blow to our collective knowlege and memory.