The user most likely to engage in retributive downvoting are those who engage in hostile debate and subsequently have low karma ratio's themselves (VoiceofRa has 68% favourability). Perhaps you could disable downvoting functionality for those with a karma ratio lower than 80%? Considering that poor quality of contributions is another big factor for low karma ratios this measure would have the added benefit that our most competent users have more power.
The question very likely was: "What charities should I give money to maximize utility?"
For about a bit more than a year I have been wanting a forum very similar to this one. In the process of gradually unsubscribing from the defaults on Reddit I found that even many of the Truesubreddits were not satisfying any longer and not knowing of the existence of LessWrong I put a moderate amount of effort in fruitlessly trying improving those subs. It took joining the Effective Altruïsm to stumble on this site, the point being that there likely is a considerable pool of potential users for this site who I suspect don't know that this site exists eith...
One person filled in a 0.51, but even corrected for that the mean is 69,76 (at 17 votes). My hypothesis would be that it has to do with the likely disproportionate percentage of users here that have Aspergers, something that is known to be associated with a poor ability to understand faces.