The addition of nullable or optional types to mainstream languages was a net good. It doesn't completely solve the billion dollar mistake, but it makes it far easier to write safe code.

For most of us anyway.

Sam found this representative line, which shows how one of his peers understand nullable types to work:

DateTime? current = new DateTime?();

I actually don't think I've ever seen anyone create an instance of the nullable wrapper directly, like this. I've never contemplated doing it. The more traditional usage would be something like:

DateTime? current = someFunctionWhichMayReturnAValueOrNull();

We don't know if we got a null or not, but because it's wrapped in a nullable type, we can still handle it safely without risking a null reference exception.

Instantiating a nullable type directly results in a nullable type that is known to be empty. Which I can imagine some uses for, I suppose, but still seems like a real weird choice. And it's unclear- if you really wanted that, you'd just do DateTime? current = null; which is a more obvious way to say the same thing.

In the end, I'm not certain this is actually a WTF, but it still perplexes me. And it's a representative line- this pattern appears everywhere in Sam's codebase, with enough frequency that it's more of a surprise when people use nullables the standard way.