If you want to increase participation on Less Wrong, converting irrational thinkers to rational thinkers is the only way.
Less wrong does not have a mandate to educate the merely interested, probably because most of that kind of interest seems temporary. The educational efforts that seem required are rarely intrinsically rewarding. And the bar for valued participation is so high, it discourages the unprepared.
Less Wrong seems to be trying to create plenty of tools for self-education on the subject of rationality, so I don't know that a mandate to educate individuals is necessary... But I do think that anyone who is compelled to reply someone at a different level of education on a subject than themselves ought to feel compelled to point out where the energy for contribution/education should actually go, instead of merely curbing the enthusiasm to participate.
Currently, LWers get +1 karma for a comment upvote, and +10 karma for a main post upvote. But clearly, there are other valuable things LWers could do for the community besides writing comments and posts. Writing isn't everyone's forte. Why not award karma for doing productive non-writing things? It's probably not optimal that karma and the community status that comes with it are awarded only for the thing that myself and a few other people are good at. For example, I really wish LW could award karma to programmers for improving LW.
The challenge is doing it fairly, in a way that doesn't alienate too many people. But there might be a workable way to do this, so let's explore.
Perhaps tasks could be assigned karma award amounts by LW editors (Nesov, Eliezer, Louie, etc.), or even just one person who is appointed as the Karma Genie.
Examples: