These laundry lists of js warts get dragged out continually, so I really have to ask: How are you people actually developing in javascript and haven't yet discovered linters?

Linters have been around for over a decade and solve all of these issues (as they do in other languages as well). They're also easily integrated in every text editor and build system I've ever seen.

And why shouldn't the interpreter support these rules? Because a linter can do this almost as easily, and not break backward compatibility.