Well, Qatar's birthrate is in a decline, too. But that's beside the point, since I don't actually disagree with you. Both your comment and mwengler's reply strike me as arguing a different point from what I was making in the essay.

I know this is tangential, but I want to point out why the statistic you used is deceptive. Qatar has a huge foreign population (80% of the population) with much lower birthrates than the native Qataris. Four kids/ woman for Qataris, and 2 kids / woman for resident foreigners. So the decline in birth rates is mainly caused by 2 factors related to immigration. The first is that the resident foreigners have relatively fewer women (most migrant workers are males) and therefore lower the "births per 10,000". Second, the women that do immigrate in have far lower birth rates than Qataris.

The more important element here that I disagree with is this:

If some people wish to have lots of children and are willing to endure having an otherwise lower standard of living because of that, that's fine by me.

There are externalities here. When people make lots of kids, it doesn't just crowd out resources for their parents. It crowds them out for everybody. At some point, more kids means higher prices (or, in a command economy, smaller rations) for everyone else. I am somewhat sympathetic to the Hansonian sentiment that having a huge number of poor people is better than having a tiny number of idle gods, and that poor people can be happy.

But I do flinch away from the idea that human-level minds should be like dandelion seeds for profligate, reproduction-obsessed future ems.