The hashing part is kind of orthogonal. The real negative outcome of quantum computers getting reliable and powerful would be that ECDSA would be broken (using Shor's algorithm variants). This would make every coin stealable by anyone with access to such a computer. Some coins would be easier to steal than others (P2PK would be the easiest - and all of Satoshi's coins are P2PK). The Bitcoin network would keep working, but coin-ownership would be meaningless.
I started reading the article assuming it was an April fool's joke. After a bit into it, I thought it was not a joke. When the self-deprecation began, I was again convinced it was a joke - but at the end of the article, I think this is not a joke. It's a rather good take on why Bitcoin maximalism is what it is.
Some degree of ETH-maximalism will be required in the future given the sheer number of pretender L-1 blockchains snapping at ETH's heels. Writing about BTC-maximalism sets the foundation for that culture.
Zero Knowledge Contingent Payments are one approach. Encoding everything that you might want to buy as an input to a ZKP system is a stretch, obviously. But at least, that's the spirit of this philosophy.
As for "Crypto-less federated systems like Mastodon and friends" - you have to ask yourself why they don't work at scale. That's the key insight of Bitcoin. You need to have a system-native incentive for the nodes to do their thing, and this system-native thing (BTC the currency, in Bitcoin's case), should have outside value. Many wiser people have said this (not on HackerNews maybe), that money is the only use case for a blockchain.
I’m not sure that Bitcoin offers any special insight here.
We use email; it’s very much a crypto-less federated system that works at scale (of, more or less, every Internet user!)
And there are newer examples: while it’s by no means a Twitter, Mastodon (and the broader ActivityPub universe) is already at a healthy scale. I collected these stats three and a half years ago; the ecosystem has grown substantially since then: https://davepeck.org/2018/05/03/mastodon-stats/
Austrians and the HN community talk past each other because it's not easy to get the latter (which I am a part of) to see that their large salaries in FAANG companies are partly due to the Fed largesse.
You mean digital signatures - and yes, we use signatures everywhere in public key cryptography.