r/the_Donald was "quarantined" by the admins, so it cannot be discovered by users in the same way as other subreddits. That cut off a lot of the organic growth that you would normally see, and it cut off users who might normally see r/the_Donald on the r/all or r/popular wander in to comment/argue. People who are not already subscribers just no longer even see anything at all from r/the_Donald.
There was some issue with sticky threads not rising as much to the r/all that impacted r/the_donald, but otherwise, I can still see posts from that sub on the front page though I do have to scroll quite a bit.
I think he’s using “quarantine” in the practical sense rather than the Reddit-specific terminology sense.
The only distinction at this point is that the subreddit doesn’t have the yellow banner or verified email on account requirement. It is quarantined in the ways that count, such as inability to hit the front page regardless of popularity.
