Just having a small amount of extra accounts can make a big difference if you can down-vote stories at the very beginning. This gives the unmolested stories a big head-start. I think that reddit implemented different behavior for the first hour of a story's life for this reason.
Only one down-vote a week? If you reduce the frequency like that, then that's just another way of weakening down-voting, which is what reddit seemingly did to their downvotes.
