Downvoted, for seemingly seeking to force everyone to waste time and space, just so that a very rare and very slight abuse of the system doesn't have the chance to occur.
Either you have other additional reasons to make you favor this suggestion (in short you'd want an explanation of downvotes to be made mandatory regardless of such incidents) and thus your suggestion improperly disguises itself as a suggested solution to this problem -- or you've just not bothered to make a cost-benefit analysis in regards to the repercussion of your suggestion. Or both.
Thank you for your comment, but sorry you missed my point, which was to consider technical solutions before social ones (e.g. locked gates work better than "no entrance" signs). The one I suggested was an example (as clearly stated in my post), not a request. Of course it goes without question that one should consider ramifications of any solution, technical or otherwise.
Oh, and please feel free to provide the cost-benefit analysis of mandatory commenting for downvoting, or a link to such, I'd be quite interested. Some issues I can think of is t...
People who go back and downvote every post or comment a Less Wrong user has ever made, please, stop doing that. It's a clever way to pull information cascades in your direction but it is clearly an abuse of the content filtering system. It's also highly dishonorable. If you truly must use such tactics then downvoting a few of your enemy's top level posts is much less evil; your enemy loses the karma and takes the hint without your severely biasing the public perception of Less Wrong's discourse.
(I just lost over 200 karma in a few minutes and that'll probably continue for awhile. This happens to me every few weeks. Edit: I mean it's been happening every few weeks for a few months for a total of only three or four. Between 400 and 700 karma lost total I think? I don't mean to overstate the problem.)