I disagree. I think responsible moderation is not only positive, but mandatory for a community to maintain any sort of quality. Hacker News is moderated (usually quite well), and it would be far worse without that moderation. Likewise, /r/science would be a shit show without moderation; and /r/science is perhaps the heaviest moderated subreddit I subscribe to, including some quite controversial ones.

I don't know that the "one sub per mod" rule would be a net win; responsible volunteer moderators are hard to come by.