kamens/khan-exercises — comment on commit a7605a3656ee88f07664a4513c5c50e2f4cde5a3
File: khan-exercise.js line 929
By nsfmc:

john mentioned in passing a while back something about how IE has a weird interpretation of `delete` on objects. I don't think this is a situation like that, but i recall the side-effect being unintuitive.