> Performance? Codegen simplicity? Why, again, must one use the syscall ABI for anything that is not a syscall?

If you can figure out an ABI that gives you significant advantages, sure, knock yourself out. But given that you're going to have to implement the syscall one anyway, if there's no compelling reason to use a different one then why make things more complicated?

> Again, why do you want the OS to get involved into any of this? It's not the OS's job, period

Again, why have a filesystem if you're not going to have any standardised structure for how to use it? Why have an OS at all if you're not going to give programs ways to interact with each other? The OS owns the filesystem, it should also define how it's used.

> stop trying to make the world an even worse place

Right back at you.