It sounds like you're trying to reapply a principle from software development to online community building?
LW has scaled. Lots of people read this site. Our last survey got over 1000 respondents. (This may not sound like much compared to e.g. reddit, but there are lots of dead little online communities that no one sees because they're dead; being dead is the default state for an online community. The relevant norm is /r/LessWrongLounge, not reddit as a whole.)
Well, the scaling problem in software development was specifically about getting a lot of users, so it seems relevant.
Anyway, if we have scaled, and we're not having Eternal September, that suggests we're doing something right.
Is that thing we're doing 'right'... keeping out the normal people? If so, that's not so great. It's important to get through to normal people.
My (inadequately stated) point was, we're much more likely to have problems attracting enough normal people than having trouble dealing with a flood of them. A little change to the header isn't going to make that big a difference.
I told an intelligent, well-educated friend about Less Wrong, so she googled, and got "Less Wrong is an online community for people who want to apply the discovery of biases like the conjunction fallacy, the affect heuristic, and scope insensitivity in order to fix their own thinking." and gave up immediately because she'd never heard of the biases.
While hers might not be the best possible attitude, I can't see that we win anything by driving people away with obscure language.
Possible improved introduction: "Less Wrong is a community for people who would like to think more clearly in order to improve their own and other people's lives, and to make major disasters less likely."