I upvote my comments - as to be seen here. Because of the ROI arguments you mentioned above plus I am much better making valueable comments than producing valueable articles.
But I never came to the idea of not voting on a post that I comment. Mostly, because I really can NOT comment any garbage post just to self-vote. It is impossible for me. I need something going, a dialogue, something I can grasp, think about and respond to. And that has to be rewarded, no matter how tiny my little cent extra is for now.
Of course I hope to find people interested in me, people that benefit from my way of thinking, so they maybe will upvote me, too. But this is only 50% of my Steemit experience. I am community-focused and I noticed only a few days after starting on the platform how important the follower-system is for this. You really form a tribe, which I consider to be the more ethical way of success in here.
Voting on my own comments isn't something I do, but I won't condemn all such behaviour. It's just a matter of personal choices. But the people who leave a comment, upvote their own comment and neglect to upvote the post are clearly only on Steemit for selfish reasons. I'd much rather have community!
Thanks for commenting.