Everything you post into Steemit, including comments, is stored. You can see the entire history of each person's blog posts by going to their page. And Steemit does a great job of getting a post to rank high in Googe Search, for posts that are about a specific topic. You don't want to make more than 4 posts a day. But you can comment all you want -- not a lot on one person's posts, but to connect with other people who have content you are interested in. There isn't a notification system, yet, in Steemit where they will know if you have mentioned them in a post. There is a link-bot that will notify you in a comment to your post, if someone has put a link to your post in one of their posts. So you can thank them! I don't see people tagging each other like they did on TSU. You can promote your posts in the Steemit chat platform (steemit.chat). Hope that helps. Here are some links:
https://steemit.com/steemit/@akareyon/a-realistic-integration-crash-course-for-social-network-migrants-to-steemit-com
https://steemit.com/steemit/@mikemacintire/your-steem-rewards-might-be-taxed-we-need-to-talk-about-the-huge-penalties-for-posting-more-than-4-times-in-24-hours