Because at least two people have requested that I add comments, I've implemented a comment system. This isn't well tested by me or anything, so if you encounter bugs please let me know about them! And please, make feature requests. To leave a comment, you'll need to sign in with a 3rd party, like google or yahoo.
Adding comments introduces some...issues. So I wasn't originally in a rush to get it done.
The first issue is trying to combat spam. There are lot's of options to deal with it. Widely used options like recaptcha are in a war of escalation with spammers. As a result they've gotten so difficult to read, I find them too hostile to non-spammers like me. I considered rolling my own Ascii Captcha - it would generate random words in ascii art, and prompt the user to enter the word generated. (In fact, I DID develop this and chose not to use it...yet...) Though a system like this would be fairly easy to break, any time spent doing it would be specific to kupad.net, and not really worth a spammers time. There are services like akismet that probably use baysian categorizers and the like to guess if a particular comment is spam. akismet is widely used right now, it's probably a good choice. Right now I don't have any of these in place...I'm hoping that since I'm requiring an openid login, spam will be reduced, though I don't actually know that it will help in anyway. I do have a simple honey pot in place. Apparently, spambots can't resist filling in form fields, and so I have a form field (no display) that must be left blank for a successful comment submission.
And what to do about anonymous users? I ultimately decided that having some kind of identity will reduce flaming. So, in order to leave a comment, you'll need to authenticate using OpenID. You'll be able to use lots of services (Google,Yahoo...) to authenticate this way.
Finally is the fact that there will be bugs. So I'm looking forward to angry friends telling me how they tried to leave a comment but couldn't. Why did I bother implementing this from scratch again?