I agree, not sure how easy it would be and if it would upset the people at the top.
maybe the total accumulated points of all time are also kept. YC doesn't erase any data. its just writing a new database query.
old query: Points = "select count(votes) where user.id = 123"
new method: "select votes, date where user.id = 123" and do some heuristic magic in the model or results datastructure.