C# does not allow generic custom operators, F# does, C doesn't, C++ does, several lisps do, but it's certainly not a common language feature. In C# you can overload most of the normal operators, but you can't, for example, define your own "~==" or overload "+=" to be anything other than "= self +"

By generic operators I did not mean custom operator tokens, but operators, that take type parameters.

Or I did not understand the relevance of your comment to my pondering.