I agree, if the intent is for pedagogical purposes (as in this case), the use of pre-increment and post-increment operators should probably be avoided. A good rule of thumb is that if you find yourself having to say "and" too many times when describing a single line -- then it's probably doing too much.

In fact, I was actually thinking more of this example:

  i = Math.floor(Math.random() * n--);

when I stumbled across your comment.

Otherwise, that's a minor criticism and it's a good page overall. In fact, it was one of the interview questions I was asked when I interviewed at Microsoft a long time ago. At the time, I didn't realize the algorithm actually had a name.