I've sometimes found that some people just don't get the jokes and as a result of the misunderstanding of the post, will mod it down as being off-topic. And this just isn't something that I want to happen to any of my posts. Another problems that arises is when I'm asked to metamoderate a post modded as being "funny." What if I don't really get the joke? I suppose I don't actually need to metamoderate it, but then, there won't be as many metamoderations to be reviewed, to determine if material that's actually funny is being modded appropriately. And the term is, I would say, the most subjective modifier. What makes me laugh just might make others groan, and vice versa.
But I suppose I'll keep doing what I'm doing. The system isn't perfect, but I'd say it's close enough to perfection for me. And I enjoy the odd comic relief here, despite the problems with it. If it hadn't been for it, wouldn't Slashdot be nothing but dry technical discussions?