I have thought a lot about reputation systems and I think that downvotes as an adaptive filter is a good way to do this, although some people might complain it creates 'bubbles' - but frankly, if you are not gaining from your interactions in discussions with certain individuals, why should you be forced to download their nonsense to your browser and waste valuable screen real estate on it? Some things are not consensus driven, and filtering unwanted content is an example of this.