> This is relevant in the context of OOP because in OOP when you talk of methods, you talk of single-dispatching, polymorphism and the Liskov substitution principle.

Which also apply to Smalltalk.

> Static methods are just plain functions tied to classes from an era when people thought having classes everywhere is actually a good idea,

Using GNU Smalltalk serialization syntax,

    Object subclass: #MyClass.

    MyClass class extend [
        myClassMethod [
            ^ 'Hello from class method'
        ]
    ]

    Transcript show: MyClass myClassMethod.

Using Java as example, I see no difference from

    class MyClass {
        public static string myClassMethod () {
            return "Hello from class method";
        }
    }

    System.out.println(MyClass.myClassMethod());

> Btw, if you're wondering from where the convention of using static methods for operators comes from, that's another relic of C++, a language not known for elegance, finesse or for being a good OOP language.

Better know C++, before bashing it.

In C++ operators can be defined as member functions and participate in inheritance resolution except for operator=.

I guess you are mixing C++ with C#.