Photo replies are one of the best parts of Tumblr. So-called "reaction GIFs" are popular throughout the internet, and especially on Tumblr's platform. However, the process to post reaction GIFs if photo replies are disabled is cumbersome and often leads to clicking on mysterious gray boxes.You may see a hilarious reaction GIF, or you may be taken to a teenager's tumblog where an Imagine Dragons song plays by default, your cursor turns into a rainbow cat, and everything looks like it's melting.

This usage pattern is taught in Bad UX 101. That's a really stupid class to take! I know David Karp didn't go to college, but I'm pretty sure he didn't audit Bad UX 101 or anything like that. Don't make your users have to enable a semi-hidden preference in order to participate in the fast paced, hustle-bustle world of online community building and social sharing.