Probably because the editor demo'd in the talk did as well. (But that still doesn't explain it.) Perhaps it's to make it friendlier and less an "intimidating code editor".

What I don't get is why the output is on the left and the code on the right (again as in Victor's talk). For left-to-right language users, a left-to-right flow of input to output makes more sense. It's not a huge issue, but still puzzling.