HN should charge people for the right to post. Even $1 a month would go a long way towards separating out the yokels from those who actually have something to contribute. I'd pay it.
So, the people here that annoy you most here can pay $1 to be entitled to annoy you, and meanwhile we make sure that people like David Heinemier Hanson and Nate Lawson and Joel Spolsky and the UX guy from Zappos and all the other interesting people who drop in to comment once or twice... never do.
The barrier is having to pay at all. When you contribute to something online you are already paying, with something far more valuable than that $1, with your time.
It also limits the speech to the voices of those that happen to be able to use the method of payment and adds significant overhead to the running of the site.
