#csharp like #python doesn't have private functions, only functions that are callable with a clunky syntax (in c#'s case, reflection, in python you have to use Hungarian notation)
So if this is what people really want, then I propose anti-sugar for all the functions you don't want your users to call and that you want to keep to yourself. Antisugar functions will be declared in cobol syntax to make sure no one can call them without a morning of typing.