> Outright wrong. You are allowed to handle POST requests in a safe and idempotent way.

You clearly have no idea about what you are discussing. The definition of HTTP verb semantics clearly defines the concept of safe and idempotent methods. You should seriously learn about the concept before commenting on discussions on semantics. If that's too much work, RFC 9110 clearly and unambiguously states that only the GET, HEAD, OPTIONS, and TRACE methods are defined to be safe. Not POST.

It's completely irrelevant if you somehow implemented a POST method that neither changes the state of the server nor returns the same response whether you invoke it once or many times. All participants in a HTTP request adhere to HTTP's semantics, and thus POST requests are treated as unsafe and non-idempotent by all participants. That affects things like caching, firewalls, even security scanners. The HTTP specs determine how all participants handle requests, not just the weekend warrior stuff someone chose to write in a weekend.