It interops seamlessly with C libraries.

Depending on what seamlessly means, Rust can also interop with C libraries. I wrapped a bunch of them.

Truly seamless because the zig compiler is also a C compiler, so the type information and calling convention works across languages at a level above any other I've encountered.

True, but I think that the person you're responding argued that rust/C integration is also seamless. (In the general discussion I'd say they're right as C to Rust integration isn't much of an problem and you can use C libraries relatively easily in Rust as well, but at the same time when talking about Zig I don't think it's fair to put it on the same ground).

It's also an unfinished language. I agree Zig is promising, but it's not confidence inspiring when the creator is still making videos debugging the compiler.

It is impossible to do C interop without a C compiler, by the way.

Seamlessly as in @cInclude("raylib.h")

It doesn't. The ecosystem is very immature and even the official tooling is very unstable. It has a bunch of interesting design ideas but at this point it's more of an experimental language than a production ready one by most metrics. (And unless it finds some kind of corporate backing, this is unlikely to ever change).

We shipped a few web apps backed by zig. It is absolutely in production.

Just because you put it in production does not mean it's production ready.