How to argue: twitter gently cautions its readers before offending them
Another field has a telling name: "possibly_sensitive." It's set to either true or false. The field indicates whether a tweet links to potentially offensive things such as "nudity, violence, or medical procedures." (If ever you wanted a snapshot of our world's anxieties in three terms, there you have it.) As a user you can check a box on your profile so that the media you link to is automatically flagged this way. If you don't, you risk having your pictures of your medical procedure marked as objectionable by an offended reader and thus put "in review," the Twitter version of limbo.
A field like this indicates the inherent difficulty of managing an enormous platform like Twitter. The only way the company survives is if it can safely ignore most of what's said on Twitter. If it had to use employees to monitor tweets, it wouldn't last a day. But in order to attract as many users as possible, it must find ways to avoid horrifying them.
There's a great deal of hedging in both the words "possibly" and "sensitive." The end result is that Twitter is putting the moral burden on the user. One person's art is another person's smut, and Twitter is not going to decide which is which--nor is it going to force you to look at the stuff. This position is both somewhat noble for its acceptance of the range of human expression and also highly expedient, putting the responsibility back on the user: We told you the picture was "possibly sensitive," so why did you look at it?