[Izmaki]

It is implemented as a valid HTTP code in the java Spring framework for everyone to support. That's how I learned about it first.

[x7467]

Same with the standard Go http package (https://golang.org/src/net/http/status.go?s=2540:2600).

[ericfrederich]

https://github.com/requests/requests/blob/3c5ecfc9f5f6fd2953...