Slashdot's moderation system was vaguely effective. Complete crap rarely rose to the top.

A great deal of high-quality commentary was buried, however, often the best and most informative. That's fairliy much par for the course.

Much the early vibe on the site came from the fact that it was simply where intelligent people were commenting online -- especially the early Free Software crowd (well, early in terms of Web 1.0 -- there was the whole 1980s and early 1990s contingent as well).

ESR (before he went fully whackjob mode), Ted T'so, Alan Cox, Bruce Perens, Rasterman, and others.

Much that group seems split amongst HN, LKML, LWN, and Google+ these days, along with some blogs.