[lmm]

Most languages have similar capabilities. E.g. in Java you can define a method called ★★★ if you want (edit: this specific example doesn't seem to work, but certainly non-ascii method names are possible). The difference is cultural; Java libraries generally wouldn't define such a method, while certain Scala libraries might.

[M8]

Example in the wild:

https://bitbucket.org/fparsec/main/src/c234349e7b738e09a1b9e...

[lmm]

FParsec is a port of a Haskell library, so not really reflective of F# culture.