It's complicated. Firstly because there are a lot of "IQ studies" that cited in places such as The Bell Curve that had utterly horrendous methodology. Second because there is a lot of cultural baggage around the very concept of IQ, as if it were a measure of someone's intrinsic intelligence rather than just measuring the result of the combination of intrinsic and environmental factors.

I think it depends on the scope of what's being addressed as "IQ". As far as I know, there are some fairly robust methods and results around IQ, but it's usually hard to make the leap from those to a sales pitch for any particular product/service/policy/program in a similarly robust way. So any given invocation of IQ in the wider world has a high likelihood of being somewhere between scientifically sketchy and outright nonsensical. It's reminiscent of quantum mechanics and epigenetics in that sense.

Yes and no. IQ isn't useful for saying anything about a particular person. However it is a consistent measure so if one group tests different from a different one we should suspect there is something wrong and look deeper.

Well below average IQ scores usually indicate serious and profound cognitive impairment (but for an individual you still have to check).

All other IQ scores indicate nothing at all.

It’s not that binary. IQ is like any other statistical measure of human characteristics - it’s very nuanced.

The IQ tests measure something and we can correlate that thing with other aspects like academic performance, other test scores, income, wealth, etc.

It’s a useful comparative metric, but it is not useful when people try to use it for things like racist bullshit.

Do you have another suggestion? Many of the criticisms of IQ seem less relevant in this context.

It's about as legit as height. Does it matter? Not really, but it correlates with a lot of interesting stuff.

People are more inclined to believe in something when it supports their cause.

taleb's argument has changed to IQ only matters for downside, not upside.

Not changed, that's always what the article he was referring to said.