the troll issue on sites like kuro5hin is one you can take care of easily by bitchslapping the accounts into modded oblivion or outright deleting the accounts, if someone on the admin staff has the balls to do so, slashdot seems to have a good handle on this problem
the problem is, there is nothing automatic about it, it requires constant human intervention: there just isn't any automated technical answer to problems of trolls (although a complaint reporting system and a mod threshold, say those who continually get below 0.5, that helps: it flags accounts for human scrutiny and judgment)
now dupe accounts are a bigger problem, because if you think about it, there is no technical or human solution to this
ip addresses don't work (dynamically assigned ips, many computers behind a firewall, spoofing, etc.)
the problem is, on a site with democratic ambitions like kuro5hin, the ability of someone to greatly influence the outcome of an ideologically contentious story is a real serious problem: there is a strong incentive for someone who loves a bad story with an ideological slant they love or who hates a good story with an ideological slant they hate to register dupe accounts and fire away
at the VERY least, rusty should implement a delay of one day on accounts to have voting abilities... this creates a damper on impulse-driven voting rage
but even combining human intuition with some well written log analyzing tools to catch lazy dupe account holders (4 accounts in half an hour with the same ip voting against a story), is a LOT of hard, concentrated work
if you think about it, a determined dupe account holder will get by any system you implement (randomize their access times, spoof their ips, use different machines: work/ home/ mobile access, etc.)
but you CAN greatly raise the bar on dupe accounts and make it very difficult for dupe account holders to do their mischief
one idea: i think rusty should implement a threshold system for voting
that is, only users who post at a certain frequency (at least a couple of posts per month, for at least a month, for example: proving they are a living breathing account with interest invested in the health of the site) and only accounts that get modded above a certain score on average (say 1.5)... those are the only accounts that should be allowed to vote on stories
again, dupe account holders can get around this, but at least it makes them work harder to do so, and that really means something: the harder it is for a dupe account holder to manipulate story outcomes, the better
rusty used have a system about allowing 0 modding of stories, and used to have a system whereby certain high-frequency, high-modded users could review and reverse hidden comments... so he has half of the code necessarty for such a system in hand already
you can never get rid of the dupes completely, but you can apply pressure with some clever ideas here and there and reduce their influence significantly, to the point where no one can rightly gripe about them, greatly increasing confidence in the site and pleasure with the experience here
and one more thing: NO MORE MOD BOMBERS!!!!!!!!
if an account never posts, and continually rates comments at 0, or 1: KILL THE ACCOUNT
i mean come on, is there a better definition of asocial activity that ruins user experience on a website?
The tigers of wrath are wiser than the horses of instruction.