I think the original suggestion is only a one-day carryover, so massive numbers of votes shouldn't be an issue.
in reply to Re: Leftover votes: wild suggestion / feature request(s)
in thread Leftover votes: wild suggestion / feature request(s)
Re subtracting unused votes: I think voting is encouraged enough at PM. Rewarding voting for voting's sake (or punishing non-voting) can lead to un- or ill-considered voting.
The current reward for the 1st five levels seems appropriate to get new people involved. The random XP for voting after that is probably not enough to cause undue influence.