I think this comes down to how you view SteemIt. Is it an investment platform? Did I invest (I haven't, but hypothetically) $10,000 to grow my money while ALSO supporting a new social platform? If so, growing my money means voting up my own posts/comments... regardless of it I think the article I commented on was worth 10% of my daily voting distribution (which I could have used to grow my own money).

From a purely curation standpoint, people frequently comment on posts they don't agree with, as part of a discussion, and in doing so should they upvote the content even though it isn't something they agree with? Meanwhile, they obviously agree with their own post...