All these replies were posted anonymously by the same person within half an hour. He could also have used one or more throwaway accounts, although succeeding as an AC helps proving his point against moderation. Although I do not approve his childish attitude and some of his rude comments, he did prove that things can go wrong easily with that kind of moderation system. Basically, the Slashdot system can work as long as the moderators rate only the articles related to something they know about. But if some of them start moderating something that looks interesting despite the fact that they know nothing about that topic, then things can and will go wrong.
All moderators have equal powers and the system is supposed to work as a kind of democracy.
Many lazy moderators who start rating the comments before reading the main article will moderate such articles up without thinking that they are redundant. I hope that something similar to the trust metrics implemented on Advogato could help. Although the meta-moderation limits this to some extent, it can easily be abused too. Another option would be to have several overlapping networks of trust. On Advogato, the trust metrics are related to software development.