Reported by Mike:

In particular, the line that reads

 void f() { foo(); } // reference type, warning not encouraged

isn't clear enough why the warning is not encouraged. In fact, it's because the nodiscard attribute is on the class type referred to, not the function foo(), and the return type is not (cannot be) declared nodiscard. I'd suggest, if you agree, an editorial change to something like

 void f() { foo(); } // warning not encouraged: not a nodiscard call, because
                     // neither the (reference) return type nor the function is
                     // declared nodiscard

would clarify the intent.

This seems like an improvement to me.