Those are tumblr tags. On Tumblr, if you want to respond to someone’s post, it goes onto your blog, which means your followers or people who visit your blog will see your response. But if you’re a regular user with a small following, not many people will see what you say. So it’s common practice for smaller users to respond to big posts like this in the tags, so that more people will see them. It’s kind of an antiquated thing that has persisted since the website first started