[racket] [slideshow/code] typesetting comments

Hi Matthew,

> The problem in your initial message isn't really specific to comments.

Good point, I didn't test it with non-comments...

> I had successfully ignored the problem for years, :) but now I've
> pushed a fix.

Thanks!

> The second comment-specific problem is also fixed, though it probably
> doesn't matter now that the other one is fixed.

indeed.

-- Éric