Yep, there are bunch of decisions that theoretically sound like they're great, but in practice don't really work any better than the alternatives. Just to be clear here, there's the moderation done by "official" moderators that will delete posts of certain nature (spam, illegal, etc), and then there's the moderation done by the users which is used to highlight or hide posts. We're only talking about the second one.
If you allow people to moderate and post, people will routinely downvote comments that disagree with their own comments.
Who cares? One person can only moderate a handful of posts anyways and there should be lots of people moderating. If the moderation system worked then this would be a non-issue. What it DOES do is punish people who participate in one way from participating in another way.
Moderation should be an occasional privilege not another channel to participate in the thread as it is on Reddit.
That's the philosophy used by the slashdot mod system, not a fact about moderation.
Also necessary. The Slashdot system forces people to think about why they are moderating and expressly omits "disagree".
Generally worthless however. No one really cares if a post is scored 4 because it's "interesting" instead of "insightful" and people have no problem modding something "overrated" if they disagree with it.
What the Slashdot system does best is create a nicely categorized thread at the end of the day that no one will read again. For people engaged in discussions it's pretty bad. Just check threads at the start of the day and at the end, you'll see wildly different posts
