C# compiler doesn’t regard “x is object” or “x is null” as null checking statements, so you get warnings if you’re using nullable references.

Also, I don’t understand the scare over operator overloading. It’s not common and it works fine with nulls too as long as it’s implemented correctly. If it’s buggy, you’re screwed for other cases anyway, it isn’t much helpful to try to fix null checks only.

I find this advice overhyped because of these reasons.