Working on 2.0. Both comment form and Filled in forms now use the same function to display math question, which is filled in and hidden by JS (if it's present). If you fail to answer it properly (either human error if no JS or template error, if it breaks JS), comment form gives you a notice and sets a cookie, so when you go back, you see the math question even if you technically have JS. Filled in needs to be 1.8.4 at least, it also gives nice warnings and sets the cookie too. All of that is in this plugin, Filled in needs to be 1.8.4 only to provide the hooks.