A year or so ago, I stumbled upon a website for yet another document language similar to YAML, JSON or XML; it was called KDL. I don't know what became of it, but it had one little feature that stood out: something they called "slashdash comments": /-. You can use it to mark code as comments, but it is scope aware.

For example, you can use it to comment out individual keywords and statements like final or implements X:

/-final class Foo /-implements Bar

But you could also use the /-- variant to comment out a whole section based on its scope:

/--public function fromInterface(int $i): int {
    return $i + 1;
}

It's just a small thing, but when I saw it, it immediately clicked. Especially in a language like PHP where "dump and die debugging" is the de-facto standard, it would be nice to have a slightly shorter and more convenient way to comment out code.

/-final class Foo /-implements Bar
{
    public /-readonly string $prop;
    
    /--public function fromInterface(int $i): int {
        return $i + 1;
    }
}