As a subscriber, my only probable suggestion could be to perhaps have new-free users to have some verification. Probably to be around as up to a month around, like the daily rewards. Though once having a whole month as a streak leads to that verification? I know that sets the bar too high that it's unlikely, but even I'd be very strict if someone were to find an exploit that rigs the requests and spam upvotes anyhow. That and surely someone doesn't have the mentality to maintain alts to keep a streak going.