If you search for a quarantined subreddit (i.e. one that is actually a step away from being banned) on the subreddit search, it won't show in the results.

If you search for a NSFW subreddit, it will show in the results. Porn subreddits are easily discoverable, and not even close to being banned.

(Try it yourself: https://old.reddit.com/subreddits/search?q=asshole&include_o... versus https://old.reddit.com/subreddits/search?q=911truth&include_... - you'll see it's not possible to find /r/911truth in the latter search.)