Knowing the problem so personally, I'm partial to throwing out voting-based comment filtering altogether and replacing it with a mix of the Metafilter and the Slashdot models: make registration an one-time $5 fee; let there be a "firehose" that isn't filtered by votes, but organized by date posted; let there be professional editors that select and curate user-posted links; and let the comments be organized by date from older to newest by default (this prevents a lot of the manipulation, as the oldest comments are usually free from manipulation, since we can't get to the thread faster, and undermine later manipulation, since usually people follow the leader comment), or, even better, get rid of comments altogether because a reliable and open forum like you had in the 1990s is something good (and dangerous) that you will never have again, or at least not without state-level attempts at infiltration.