"I'm doing it in Dart because it's fun." -Notch

Over TypeScript? I imagine for JS based languages the main draw is portability.

Is notch a HN member?

None of the usernames he usually uses seem to be registered. He does respond frequently on Reddit. Maybe there's an equivalent thread over there? He seems to be too busy coding to respond to any comments at the moment, though.

he just said on the stream he "likes HN but doesn't hang out on HN because there's too many nerds"

It's funny when nerds don't like other nerds for being nerds. But so typical of human nature...