Comments from feedback form - "What do you think of this page..."
It's not so much a question of the existence of a threat as it is the seriousness of the threat. Paraphrased: "I'm going to make a giant wooden hand, cover it in pubic hair, and then push it over on you at your doorstep" isn't the most serious sounding threat in the world.
Here's a serious sounding threat, as an example: "I work at an ISP. I'm going to use your IP to hunt down your RL name and address. I'm then going to go your house in the middle of the night and make sure you're home. Then I'm going to bar all the doors. Then I'm going to toss a firebomb through a window. Then I'm going to sit on your lawn and laugh while you scream."
That's a far more serious sounding threat, because that's realistic enough that even if the author of the threat has no intention of carrying it out, it may well still cause angst to the recipient of the threat. And that's the real test. Is the threat of a type that might cause real worry to the recipient, or is it just part of a trolling flamewar? There's a difference between the two, and they should be treated differently.
And indeed, "humorous" is not part of the test of what's allowable and what's not. I was thinking about "seriousness", but wrote "humour" due to the fact that there is a bit of crossover between the two concepts in my mind (ie, a post wouldn't be funny if it contains a serious threat).