I've had reports of Add Reader Comment not working like it should. Most notably it seemingly chooses a random diary to actually do the addition. I'm not totally sure why this is, but I have put some extra tweaks in place to ensure the integrity of the comments system and I hope it'll kick it into touch.
When adding comments please make sure that the confirmation page says you are adding to a diarist that you expect. If its not, try pressing CTRL-F5 (if you're using IE) and see if it reverts properly. If it doesn't do it even then, mail us with as much detail as you possibly can.
Also, you may see a 'Cookie Eater' screen when adding a comment for the first time since Friday last week. This is part of what I believe has gone wrong and the cookie eater screen is trying to clean the mess up.
I should say that I believe this is a system failure and not a crack attempt of any kind.
Let me know how you get on, and sorry for the aggro... I really love PHP, its such a class piece of software to write web pages in. NOOOOT!