Well no, I don't believe it harms steem in anyway, but as far as steemit goes then I think it does a lot of damage. The concept of steemit is to serve as a platform to reward creativity so when people power up and shamelessly upvote their posts, comments and replies, it devalues the entire system.

Now this is not to say that people shouldn't upvote themselves, no, if you make a post then you have every right to do upvote your post, but making it a habit to upvote yourself 30 times a day is doing nothing but raping the steem reward pool.

Imagine if musing decided to continuously give itself 100% upvotes till it's voting power reached 0, it would make steemit look like a mediocre site where you can make an investment then get it back by continuously pushing a button.

As far as the steem blockchain goes, I don't think it does any harm but the idea and concept of steemit is brought to shame when people do such.