Anything that can be done to encourage this feeling of intellectual discourse is a win, in my opinion.
I'll probably never get around to supporting bold text in comments either, for the same reason.
To some extent news.yc is protected by being about a topic only a small number of comparatively smart people care about. With any luck we'll never have the full-blown trolls you find on general news sites. I have some ideas for solutions if trolls do start to appear.
I've joined well over 50 social networks and what I've noitced is that freedom to choose appeals more to people than the right choices already made for them. More features, more niches, more startups, more choice. Users might complain about features, but fundamentally they like choice.
The more time a user spends making choices on a network, the more loyal he or she becomes. You don't spend 12 hours of your life customizing your profile if you don't plan on sticking to it.
Lastly, too much of anything is bad. The state should have control over medical supplies, education and energy. But beyond that, it should trust the consumer with running the country.
1. Ignore it
2. Downmod it
3. Write a quick reply
4. Write a thoughtful reply
Option 4 is ideal, of course, if you have the time, but you usually don't. Quick replies are what we want to avoid. That's how flamewars start. Ignoring the post is going to be unsatisfactory for the flamewar-prone. That leaves the down-arrow as a sort of relief valve. So I think its presence can actually reduce nastiness.
I suspect the ability to successfully transition from this honeymoon period to moderate popularity will become a defining battle for a certain class of social web start-ups.
I do see your point, though, wrt top users not spamming the site. That's largely why I liked your idea of throttling submission rates based on karma. New users should have to develop karma by being useful, rather than just prolific.
I know I suggested it, but throttling submission rates based on karma might not be fair to the end users. Once a karma-archy is established, the rich will get richer at the expense of the poor.
One solution to older users having a perpetual advantage would be to implement some sort of aging of karma, or at least of the karma value used to determine throttling. Such a thing would actually be a win in terms of SNR--it doesn't really matter how karmic someone was a year ago, if they have only made low-quality posts/comments in the past month, they should be treated (in the submission system) as a low-karma user.
The problems, of course, are that there is some fixed point, and also that news.yc may not fit the growth model that makes the above true for a community like Reddit--and that may be a good thing.
Points, or karma, could be rewarded based off a ratio of useful contribution to total contributions instead. Such a system would encourage a user to make sure his contributions to the community are good. This would be beneficial implemented in any crowd-generated news site.
While not another news aggregator, our project is addressing similar types of issues in other channels. I am loving the applied relevancy to here already.