You are just describing more tradeoffs. Look we all agree that there’s insufficient consideration of tradeoffs and there are strictly better solutions.

> DNS is mostly public and therefore shouldn't be used to hold non-public information.

This is just not true if someone is coming from enterprise IT, where DNS requests stay within the corporate network, or if MDM solutions enforce the use of DNS over TLS/HTTPS. I could see it as an honest mistake when someone came to implement this from a different background.

> The secondary issue is they used low-entropy guessable DNS records at that.

The DNS records do contain an unguessable part and they aren’t low entropy.

I get the sense that people on HN just like to dunk on the guy who came up with the design. We should always blame the processes such as insufficient review that lead to this bad outcome. Next time when you make an honest mistake because you didn’t know about something, you should also be treated with respect.