Most people upvote their own posts, but are not so quick to upvote their own comments. I've upvoted my own comments occasionally, but I don't make it a practice.

Every upvote drains your voting power, so if you upvote yourself at 100% voting power, it goes down to 97%. Upvote yourself again, then 96%. After upvoting yourself 12x on a bunch of your own comments, you'll find yourself at around 60% or so. By the time you get to upvoting somebody else, it will only be worth about HALF of what it would have been. So you are depriving others of more valuable upvotes, since you've already spent it on yourself. What I've learn on Steemit so far? Selfishness will not get you very far.

Keep in mind, steemit is all about building your reputation. If all anybody sees about you is that you upvote your own comments, it will be more difficult to encourage people to upvote YOU.

@ironshield