Following discussions about CWG2555

Consider

struct K {
  void f(this K); //#1
  void f(); //#2
};

Here, exactly one (#2) function has an implicit object parameter and no ref qualifier, and after removing references, both have the same type (K) - per https://eel.is/c++draft/over.match.funcs#general-4 - although whether this rule applies could be clearer.

So #1 and #2 correspond, even though they do have different object parameter type (K and K& respectively)
All compilers reject that code.

However, consider a very similar example

struct OK {
  void f(this OK);
  void f() &;
};

Here, no overload has "an implicit object parameter and no ref qualifier" so references are not stripped, we compare K and K&, which are not the same type, the parameter do not correspond and we can declare a distinct overload.

What makes us want a different outcome in both scenarios, when the model is that the lack of & does not implies by value?