There is nothing wrong with voting for your own posts, it's well within your rights to do so, however there comes a point when it becomes blatant abuse. For example, you are allowed by the system of steemit to upvote your comments as well, but if you were to say, spam hundreds of one word comments on old and irrelevant posts and then 100% upvote them yourself that would be seen as abuse, since you are not contributing anything to the system, only taking from it. Haejin's posts are seen as abuse because of the sheer amount of them. He could EASILY combine them all into three or maybe even four posts per day, but he posts like ELEVEN per day. The reason he does this is because he can maximise rewards that way, and take more of the community reward pool for himself. He also doesn't do anything to engage with the community here, just take from it. Anyhow, the main point is: Voting for your own post is totally ok, abusing the system by posting a ton of low value and then upvoting it yourself is not ok.