Self upvote of comment is to attract attention and jump over all the thanks posts.

There is definitely a gray area of what is overvalued. A model could be developed comparing Steemit Article Quality verse Freelance Writers. I do not even know what freelance earns per article but I am sure someone knows the answer.

There are definitely some black and white cases. The other day I saw a post commenting on one individual with $28 comment self upvotes which were all just thanks or other spam.