I've defined it myself (when doing C# with functional heavy code but it feels clunky) but there's still edge cases where it isn't as nice especially with functions of multiple args, or functions passed in. Sure C# can do these things with more code, just like F# can jump into some unsafe code, but its nicer in F# IMO. The other thing is that the operator as above is probably allocation heavy especially when needing to complete a function inside the lambda whereas the pipe in F# the compiler just rewrites the code. In hot loops or highly repeated workflows this makes a difference.

C# Fluent API's aren't really piped things since they usually just mutate a variable underneath (hence the ignore often at the end of them in F#). I don't think fluent API's and piped functions are the same thing, and the pipe operator allows any function that matches the signature to be put in.