why is it that any mention of Rust on the internet will bring about these wildly-overshooting claims. The amount of production software having been re-written in Rust (or replaced by a Rust counterpart) is minimal. This kind of rewrite is rare for any programming language. Yet claims like this are everywhere.

I thought it was a troll comment.

I find it annoying either way: it doesn't provide valuable/novel information and isn't conducive to productive conversation (in part because it's unclear if it's sarcastic or earnest)

If you're going to write a whole kernel in Rust, why would you settle for making a copy of Linux? Bug-for-bug compatibility with 30 years of cruft isn't exactly exciting or even necessary.

Imagine the number of developer years required for even just parity…

I think it is a Ship of Theseus situation. Once Rust becomes acceptable in the core kernel, module by module, it is going to spread.

I am fully Team Rust for core infrastructure, but I am curious how many security blunders in the kernel are memory errors vs bad security architecture.

20 years, 1000+ devs. Just a guess.

Sort of. Is the Linux kernel huge and has an amazing number of man years in it .... certainly.

If starting over from scratch could you ignore most architectures, drivers, etc and support current hardware ... also yes.

A new OS could skip 32 bit mode, alpha, mips, itanium, loongarch, 68k, pa-risc, powerpc, s390, superH, sparc, parallel ports, serial ports, supporting zillions of PCI/PCIe cards that you can't buy any more, messing around with archaic 16 bit bootloaders, etc.

In the same sense that the heat death of the universe is "only" a matter of time, perhaps.