It&#x27;s the social &quot;flows&quot; of the sites that differentiate them. On Reddit, you subscribe to a number of communities, and then you only see content that a bunch of people agree fits those communities&#x27; standards. On Tumblr, you subscribe to a bunch of individuals&#x27; blogs, where those bloggers all have 1. a very simple&#x2F;encouraged inbuilt mechanism for sharing things they see from their own subscriptions onto their own blog, and 2. a culture of &quot;signal-boosting&quot;—a term loosely meaning &quot;passing along chain letters&quot;, or more generally, sharing something they wouldn&#x27;t have posted for its own sake, with an audience that didn&#x27;t sign up for such content, because &quot;it&#x27;s important that this spread until it reaches the people who are affected by it.&quot; As if it were a local weather emergency or an amber alert or something.<p>The combined result is that, on Tumblr, you&#x27;ll subscribe to people for one thing, and then inevitably they&#x27;ll &quot;signal-boost&quot; other things into your feed that you didn&#x27;t sign up for. The most often &quot;signal-boosted&quot; thing is Social Justice discourse. This is why people get the impression Tumblr is a Social Justice website: if you subscribe to blogs about porn, cats, and tech, you&#x27;ll end up with a dashboard containing porn, cats, tech, <i>and</i> &quot;signal-boosted&quot; Social Justice.<p>Personally, my problem isn&#x27;t with Social Justice, but with &quot;signal-boosting&quot; itself. I (very carefully) use Tumblr, and enjoy doing so, but only by strictly following a policy of unsubscribing from any blog that &quot;signal-boosts&quot; anything. I think this means that I end up following only blogs that are completely disconnected from Tumblr&#x27;s social graph, though, so I don&#x27;t know how precisely I can be said to be &quot;using Tumblr&quot; at this point, rather than just being subscribed to some blogs that happen to be hosted there.