I think LessWrong actually has a higher barrier for contribution -- at least for articles -- because you're expected to have 20 comment karma before you can submit. This means that, if you're honest anyway, you'll have to spend your time in the pit interacting with people who could potentially shout you down, or call you a threat to their well-kept garden, or whatever.

I have at least 3 articles in draft format that I want to submit once I reach that total, but I don't comment on discussions as much because most of what I would say is usually said in one comment or another. For people like me, the barrier of "must email someone" is actually easier, since discussion contribution requires a sense of knowing how the community works, intuiting a sense of what the community deems a good comment, and posting along those lines.