Credit @ Bardfinn

Reddit's administration has a hands-off policy, meaning that they are not actively moderating content on subreddits, unless they are forced to do so (by various mechanisms). In plain English: By and large, Reddit admins are not reading, and not moderating, what people post to subreddits. That's why they have Moderators.

T_D has been actioned three other times in their existence that I'm aware of, and each time they've moved away from the issues that Reddit administration brought up with them. Mainly, T_D is "tolerated" by Reddit administration because Reddit administration wasn't getting abuse reports through the report system. 1/3rd of that was because the T_D mods disabled reporting via CSS changes, and 1/3rd of that was because no one banned from T_D could hit "Report" on a post or comment on the Desktop interface, and 1/3rd of that was because no one wanted to bother to do T_D mods' jobs for them, and scroll through their New and Comments queues, and fill out http://www.reddit.com/report. Also, because there was no journalistic coverage of the content. So, when someone started going through their New queue and Comments queue and reporting material that violated the Content Policy, directly to Reddit admins (which can be done by filling out http://www.reddit.com/report, or sending modmail to /r/reddit.com)

The admins had direct, first-hand, red-flag knowledge that the subreddit had content in it that violated the Content Policy. They Quarantined the subreddit because it's SOP for Reddit administration to Quarantine subreddits where they consistently must take moderation actions because the moderators will not take action, or have demonstrated a willingness to ignore the part of the Reddit User Agreement Section 7 : You agree that when you receive reports related to your community, that you will take action to moderate by removing content and/or escalating to the admins for review; So, to RECAP: T_D "moderators" weren't being babysat because Reddit admins don't want to babysit any community - which can be called "tolerating"; T_D "moderators" sabotaged the proper operation of their community and violated the Reddit User Agreement Section 7; People posted content to T_D advocating for armed, violent political insurrection and political assassinations; Journalists wrote about it; Reddit administration was in a position where they could not claim that they were unaware, and therefore executives had to take action to enforce their User Agreement. The Moral Of This Story: Reddit Administration isn't tolerating the existence of T_D -- WE ARE. If people spent time reporting content on T_D that violates the User Agreement / Content Policy / clearly aids & abets violence -- to both Reddit Administration and to journalists -- then Reddit's administration would be forced to act.