HAHA, there is no such thing as free promotion. There is a lot of money to be made in real advertising. What you are describing is vote selling to get on trending pages that only noobs and trolls bother looking at (I think I fit into both those categories).
I only comment these days, writing posts or in my case making videos is not worth the time.
Oh yeah, I like to downvote the shitty posts on trending. It is so funny to see how angry people get over losing less than 0.005 Steem from my pathetic downvote.