This particular subreddits mods wanted to get more subscribers (their reason being they were almost at 30k subscribers). They made an advertisement of sorts and put it in another, larger, mainstream subreddit. They prepared for it. And all the new content and comments were heavily moderated. The regulars also helped the moderators with reports for those comments against the rules.
Another good example of heavy moderating is http://www.reddit.com/r/askscience . They don't tolerate any crap. Jokes, anecdotes, or off-topic posts are quickly reported, downvoted, and deleted. Most questions are labeled to the pertinent field. They are also a default subreddit.
This is pretty much it. There are some important cases I could point out to this as well. For example: http://www.reddit.com/r/redditgetsdrawn/comments/1z9fco/atte...
This particular subreddits mods wanted to get more subscribers (their reason being they were almost at 30k subscribers). They made an advertisement of sorts and put it in another, larger, mainstream subreddit. They prepared for it. And all the new content and comments were heavily moderated. The regulars also helped the moderators with reports for those comments against the rules.
Another good example of heavy moderating is http://www.reddit.com/r/askscience . They don't tolerate any crap. Jokes, anecdotes, or off-topic posts are quickly reported, downvoted, and deleted. Most questions are labeled to the pertinent field. They are also a default subreddit.