What is this catchphrase word salad trying to convey? I can see exactly what you used and didn't use, in your one sentence long comment above. Why assume that you're being quoted at all?

Empty interfaces or "marker interfaces" are allowed by the c# language: public interface IDoNothing { };

But no style guide will recommend them, and they are seldom seen in code, as there are better ways to accomplish the same thing. So they're technically there, but are usually overlooked, that's all.

Single-method interfaces are common, and are roughly equivalent to a function pointer.

Multi-method interfaces are also common, and are not.

It's not about you.