> This did not improve performance, it was just an unnecessary hack

Well, the Android VM certainly uses a signal mechanism for safepoints and stack overflow checking, for a reason (https://android.googlesource.com/platform/art/+/master/runti...) (both latency and code size), so don't sit there and tell me that the VM running the world's most popular OS is pessimizing itself pointlessly.

> The kernel handles hardware traps, which may or may not lead to UNIX signals.

Not all traps result in signals, and not all signals are traps. Nevertheless, the POSIX signals API is the means through which Unix OSes provide user programs the ability to interact with CPU traps. (Windows does the same thing, morally, with SEH and vectored exception handling --- https://learn.microsoft.com/en-us/windows/win32/debug/vector...). Any decent OS should provide applications with the tools they need to make full use of the underlying hardware. All these anti-signals people are just arguing that programs be bigger and slower, because they can't make full use of all the hardware features of the system, out of, ultimately, an aesthetic objection to signal handling.