Ok, i see what you are saying...but, if we foster a community where comments are content relevant and not up-vote beg spam like "great post". If we each take the time to write meaningful comments and actually contribute to a discussion then the comments section becomes a value proposition for the reader. People are more inclined to pay attention, read, and up-vote quality comments. If the top comment is a self up-voted misspelled irrelevant piece of garbage, chances are whoever is reading will simply stop right there. Consequently the only use case of self up-voting would be if you are certain your content contributes something meaningful to the community, which one person simple cannot determine you=/=the steemit community.