I will answer only the last part: Vote selling hurts the steemit platform far more than anything else. Vote buyers are greedy or ignorant of the long term effects of their actions. Voting is to the advantage of both the voter and the user being voted. If no one is buying votes, the sp holders would still have to vote in order to enjoy the benefits of curation as well as for the value of steem to appreciate.
I will answer only the last part: Vote selling hurts the steemit platform far more than anything else. Vote buyers are greedy or ignorant of the long term effects of their actions. Voting is to the advantage of both the voter and the user being voted. If no one is buying votes, the sp holders would still have to vote in order to enjoy the benefits of curation as well as for the value of steem to appreciate.