alt Hacker NewsHis point is literally that writing a JVM (or any other language runtime) in Rust is unpleasant.
He can't write a JVM without using unsafe. So his disagreement on the "table stakes" is that his "table stakes" require using unsafe Rust everywhere and from that perspective Rust is not that different from any other language.
Hence the complaint about the lack of universality, which I personally consider weird. His point is that you cannot write the most interesting low level programs using just the safe subset of Rust.
If you have to write unsafe Rust (emphasis on have, your mileage may wary lot on that), then you have to litter unsafe everywhere in your code base so how does Rust help him? That's his point, but he doesn't want to say it out loud.
What makes a JVM a good fit for a low-level language is the need/utility for precise control over the hardware, but that's always the reason to want a low-level language (why would you use a low-level language if you don't want precise control over the hardware?). When Rust gives you safety it takes away much of that control, and when it gives you control it takes away the safety. Now, there could well be cases where this mix is fine - I've never worked on a browser, and Rust may well be the best language for writing browsers.