No system will be free of problems or gaming.

But, doesn't hacker news actually have implicit down voting by way of time? HN isn't designed to be a searchable Q&A or forum. It's a "what's a currently popular" site. If something isn't good, it just disappears faster than the opposite.

Have I wished I could down vote things sometimes? Sure. But then I just wait 5 minutes, refresh, and it's gone.