I disagree that hn's is the worst. Slashdot has a fancy system because the signal to noise ratio is so low there. Even reading at the maximum post "quality" level of 5 there is a lot of spam, off-topic banter, lame humor, etc. In comparison, I find the S/N here to be orders of magnitude higher. I think the reason that is so is that the HN system encourages certain behaviors which lead to better discussions whereas the slashdot system is more of a passive filter on a noisy feed, which is inherently a losing battle.
In theory I have a slashdot account that's about a decade old, I have forgotten the password and no longer use the email address it's attached to. I haven't bothered going to extreme efforts trying to recover it (e.g. searching out old password lists I have written down somewhere) nor have I bothered creating a new account. Discussion on slashdot is just not worthwhile, at best it's like trying to have a conversation by yelling across a boisterous lunch room, at worst it's just spitting into the wind (which tends to be the average case). There are so many better alternatives out there now it's really not worth the time to visit anymore.
I think the reason that is so is that the HN system encourages certain behaviors which lead to better discussions whereas the slashdot system is more of a passive filter on a noisy feed, which is inherently a losing battle.
HN survives mostly by being small, self-selecting, and somewhat obscure. Slashdot, for all its flaws, is remarkable for being large, well-known, and of consistent quality. Most comparable sites would be well on their way into the gutter at a quarter of /.'s age.
I'm aware of only three viable means of maintaining stability in an online community: slavish adherence to the Peyton-Jones Law (viz. "avoid success at all costs"), iron fist moderators and a tangible cost to participate (cf. the Something Awful forums), or whatever secret sauce /. has.
HN almost certainly doesn't have the third, and the Powers That Be have better things to do than implement the second. I seem to recall pg describing the slow growth of HN membership in very positive terms, so I'm pretty sure there's a deliberate strategy here.
In theory I have a slashdot account that's about a decade old, I have forgotten the password and no longer use the email address it's attached to. I haven't bothered going to extreme efforts trying to recover it (e.g. searching out old password lists I have written down somewhere) nor have I bothered creating a new account. Discussion on slashdot is just not worthwhile, at best it's like trying to have a conversation by yelling across a boisterous lunch room, at worst it's just spitting into the wind (which tends to be the average case). There are so many better alternatives out there now it's really not worth the time to visit anymore.