although it's a good idea, i don't think that a POST rating system would work on this site. The moderation feature of slashdot is in place to weed out the huge amounts of stupid and bullshit posts and put the posts with the most relevance in plain view.
The reason that it wouldn't work here is because, like it or not, i would say 80% of the posts made are total bullshit. That would leave VERY few posts to read if all the bad ones were hidden because they were useless (i am assuming that the rating/moderation system would be the same as /.).
Also, we have our own moderation system. Bad posts are deleted unlike slashdot. Crap posts on /. just end up with negative points and are filtered out by most users settings.
Now, what i think would be a better system would be a USER rating system, where instead of rating posts, you can rate the user themselves. Similar systems exist on the nsmb.com and overgrow.com websites. On overgrow, users can give other users Karma points, and on North Shore Mountain Biking you can vote for a person, and their average rating is displayed alongside their name, post totals etc.
This way, matt could develop some more user settings and allow you to actually filter out posts from just certain people.
go check out the aforementioned sites to see what i mean.
Six Million Ways to Die, Choose One