1. It doesn't solve any problems of group think, because if pg and the Y Combinator folks think the system is already tilted toward a certain group and set of beliefs - this now empowers them all as citizen moderators.
2. It further empowers this group by giving them the ability to remove other members of the group's ability to moderate comments.
3. It increases the "cost" of commenting far more than most other moderating proposals would. Not commenting on a popular post? Why bother. Continuing a conversation in replies? Again, why bother.
4. It had such a poor specification that cperciva found a critical flaw in the implementation details in mere minutes. If pending comments is an answer to a problem, then it was not the sort of answer that would have been approved by this comment system.
Who wants to contribute to a "community" where there is active censorship of posts critical of YCombinator companies (see Dr Chrono), or you get hell-banned for no good reason, and now this poorly thought-out "rule"?
CPerciva pointed out an obvious flaw. Another is this: if you had to start a brand new HackerNews tomorrow, would you implement the rule? Of course not, because nobody would have any karma points to begin with, so they wouldn't be able to approve or see pending comments, meaning no comments would ever get posted! Duh!
Now you could argue that the HackerNews moderators and owners have karma points and they could approve comments to seed the system... but then why not just have a private forum for all your start-up friends, invite only, so you can be sure they all speak right?!
I think that once I break the habit of typing "news.ycombinator.com" when I open a browser I won't miss this place very much.
I prefer to think of them as the high priests; only they get to decide what constitutes divinely ordained Truth.