Author here, my bad. There was a DoS attack against this a while ago and I set too strict limits after that. Didn't expect it to hit Hacker News again. Should be fine now.
What makes someone attack this?
I'm running an online game on the side and am thus commonly the target of DoS attacks. I guess it's related to this.
You mentioned in your blog post that you know who the attacker is. Do you know their motivation?
Destroying the fun for others and wasting time I figure. I received no demands or anything like that.