I don't see a problem with people using the Steem Power they have earned/bought to upvote themselves.
Obviously the bigger the account, the more questions one will receive.
Morally not an issue.
Is the activity of self-voting good for the platform? I don't think many people will come to SteemIt to watch a group of people vote and self-vote for themselves and each other. Who knows, it is a balance we are trying to find. :)
Interesting post.
OK, we already see that many comments mean many different opinions. I linked the article of @dirkzett who upvoted his own comments after what another user told him to him flag him if he wouldn't stop doing that. We see the topic is rather complicated ...