I agree that strong moderation is key, but reddit's moderation system doesn't encourage strong moderation and is pretty borked in general. Strong moderation is a rare exception, especially when you consider the more popular subreddits have thousands to hundreds of thousands of users per moderator.

For one thing, the site admins won't get involved with what they term "moderation fights" so one bad actor as a mod can cause a hostile takeover/coup of a subreddit that nothing can be done about.