Maybe there could be a rule that parameters have to be named only if their type doesn’t already disambiguate them and if there isn’t some concordance between the naming in the argument expression and the parameter, or something along those lines. But the ergonomics of that might be annoying as well.
let warn_user ~message = ... (* the ~ makes this a named parameter *)
let error = "fatal error!!" in
warn_user ~message:error; (* different names, have to specify both *)
let message = "fatal error!!" in
warn_user ~message; (* same names, elided *)
The elision doesn't always kick in, because sometimes you want the variable to have a different name, but in practice it kicks in a lot, and makes a real difference. In a way, cases when it doesn't kick in are also telling you something, because you're crossing some sort of context boundary where some value is called different things on either side.