I've been thinking about pending comments and some of the issues I foresee from it. I have a major suggestion on how to change pending comments functionality to make it more useful and keep comments productive:

The basic idea is to move away from the model of censorship/moderation and toward a model around rate limiting, as well as to integrate more seamlessly into the existing workflow of HN rather than to bolt on new things for people to do that cause the site to break down if they're not done.

So, instead of hiding pending comments and making them visible only on the pending comments page until they've been upvoted enough to graduate to real comments you show them inline, but not 100% of the time. There are lots of algorithmic options on this part but one simple idea would be to display them to X% of users with over 500 karma who have been active within the last few days. The posts would simply appear as normal, and have normal up/down vote buttons on them.

If the post gathers enough upvotes then it gets promoted to universally visible. If not then it continues to be only partially visible until some timeout where it becomes visible.

Additionally, the amount of upvotes/downvotes could change the rate limit timeouts on the post. If a post receives a few upvotes then it could be automatically promoted out of pending status faster than one with no upvotes. If a post receives a few downvotes then it could be promoted slower than normal. If a post receives enough downvotes then perhaps it disappears, or simply takes a very long time to show up (days? a week?)

The advantages of doing it this way are many fold. It blends into the normal functioning of the site. People won't even know they're voting on pending comments, they'll just use the site as usual. More importantly, it gets rid of a lot of the clunkier problems of pending comments, such as the potential for comments to languish in the pending state. In that case this model simply falls back to the rate limiting model. The site would still continue to function just fine even if nobody voted on pending comments, but the pace of discussion would be slower. And it avoids the censorship problem. Moderation is a fundamentally hard problem even with humans in the loop, by defaulting to allowing all comments to surface eventually you solve the problem of denying people a voice while also putting the brakes on overheated emotionally fueled flame wars and so forth.

Also, I'd propose a few tweaks. First, make it so that high karma users' comments usually skip the pending step. To me this just seems logical and a good way to avoid excessive friction. If necessary you can add a toggle which forces pending comments behavior on a per thread basis. Also, you can add functionality which pushes a comment into pending status if it's downvoted. Second, consider making direct replies always visible to the parent poster, perhaps gated based on karma of the parent/child or both. Third, perhaps make it impossible to reply to a pending comment unless it has at least one upvote. That would preserve constructive back and forth comment threads while discouraging flame wars and vitriol.

I don't want to see commentary, even controversial commentary, squashed in a misguided effort to turn HN into the digital equivalent of "Pleasantville". Sometimes controversy leads to extremely valuable discussion. But I think discouraging and quieting non-constructive commentary is well within the realm of possibility.