The thing Tumblr does that&#x27;s unique is: to join the comment thread you have to have a blog, and your reply goes on your blog (and includes an automatically generated reference to the blogs of each of the other people in the thread).<p>That may sound odd and awkward and in many ways it is, but the consequence is that every conversation connects you to many other people to &quot;follow&quot;. And then the posts you get from them on your dash connect you to others. So with Tumblr, it&#x27;s extremely easy to form &quot;communities&quot; - and to find them.