Not sure if this applies to Eliezer's debate threads, but not having downvotes is a horrible setup for a debate. Every stupid comment is either ignored, which seems like "silence is consent", or starts a flamewar. There is simply no way to reduce noise.

There is no way to reduce noise for everyone else. For myself I've adopted a strategy of using the 'block use' feature whenever I encounter a comment that I especially wish to downvote. These days I consider 'block' to be a far more critical feature than downvoting is (despite remaining a big fan of downvoting liberally).