I have come across more than a handful of people who don't excel in traditional IQ tests, but who are nevertheless very capable of presenting coherent, well-argued insights. Does it matter to me that their IQ is 132 instead of 139? No. Who cares about the average IQ among members of the LW community as long as we continue demonstrating the ability to engage in thoughtful discussions and generate valuable conclusions?

Another possibility here is that your perceptions of intelligence levels are really off. This isn't too unlikely as I see it:

I've heard reports that people with super high IQs have trouble making distinctions between normal and bright, or even between moderately gifted and mentally challenged. I frequently observe that the gifted people I've met experience their own intelligence level as normal, and accidentally mistake normal people for stupid ones, or mistakenly interpret malice when only ignorance is present (because they're assuming the other person is as smart as they are and would therefore never make such an ignorant mistake).

If the intelligence difference you experience every day is 70 points wide, your perceptions are probably more geared to find some way to make sense of conflicting information, not geared to be sensitive to ten point differences.

As a person who has spent a lot of time learning about intelligence differences, I'd say it's fairly hard to perceive intelligence differences smaller than 15 points anyway. The 30 point differences are fairly easy to spot. A large part of this may be because of the wide gaps in abilities that gifted people tend to have between their different areas of intelligence. So, you've got to figure that IQ 130 might be an average of four abilities that are quite different from each other, and so the person's abilities will likely overlap with some of the abilities of a person with IQ 120 or IQ 140. However, a person with an IQ of 160 will most likely have their abilities spread out across a higher up range of ability levels, so they're more likely to seem to have completely different abilities from people who have IQs around 130.

The reason why a few points of difference is important in this context is because the loss appears to be continuing. If we lose a few points each year, then over time, LessWrong would trend toward the mean and the culture here may die as a result.