"How can LessWrong maintain high post quality while obtaining new posters?  How can we encourage everyone to read everything, but not everyone to post everything?  How can we be less intimidating to newcomers?"

A lot of Meta conversation goes on here, and the longer it goes on without having a great example to learn from, the longer our discussion will be more aimless and less informed than it could be.  Consider speculating whether blue mould from bread could treat supporating eye infections before you knew it also treated supporating flesh wounds...  it would seem pretty random, and the discussion would be fairly aimless. 

But LessWrong.com is the first successful community of its kind! There is no example to learn from, right?

With the latter, I wouldn't agree: http://mathoverflow.net

[What I've already said in comments:  MathOverflow is a Q&A forum for research-level mathematicians, aimed at each other, created by a math grad student and a post-doc in September 2009.  As hoped, it expanded very quickly, involving many famous mathematicians around the world.  You can even see Fields Medalist — the math equivalent of Nobel Laurate — Terrence Tao is a regular contributor (bottom right).]

MathOverflow awards Karma for good questions and good answers, it's moderated, it's open to new users, and maintains a high standard so professionals stay interested and involved.  Sound familliar?  Well, what about these features...

The top of every page links to:

• Frequently Asked Questions
• How to write a good MathOverflow question
• meta.mathoverflow.net, a separate forum for questions/suggestions about site policy.

Have a look at those links.  If your first reaction is "Sure, precise guidelines worked for a professional mathematics Q&A site...", consider this:  they didn't start out as a professional mathematics Q&A site.  They started out wanting to be one.  They had to defend against wave after wave of undergraduate calculus students posting for homework help.  They had to defy the natural propensity of the community to become an open discussion forum for mathematicians.  I watched as these problems arose, were dealt with, and subsided.  For example: