"Notch coding in JS" is a bit more descriptive than "trying jsfiddle", specially since it looks like code posted after the fact. A minecraft-like env rendered on canvas with it's own mini-3d-engine is amazing nonetheless :D
"Trying jsfiddle.net" was in reference to his previous tweet, the previous host he used crashed under the load from his twitter link. He wasn't "trying jsfiddle.net", he was "trying jsfiddle [as an alternative to the previous host that crashed]"
