The forks finally broke in. After six months or so.
I'm not sure why; like some other suggestions, maybe it was the installer's fault.
What happened the week before, on a recent errand, is that without any spring/dampening, going over a bump at an angle is hazardous with the forks, and as I almost slid out when this happened, I got frustrated with the forks, which up to now had been acting like a solid front end. When parking, partially out of frustration, I hit the curb with the front wheel at an angle, knocking the wheel out of alignment. So I twisted the forks back into line.
A few days later, I was riding and felt something unusual going over bumps. When I parked, I leaned against the front end with the brakes on, and sure enough, the forks are now sprung. I no longer have a solid front end. This happened suddenly, not gradually. Since I've been doing this check periodically every few times I ride the moped, I know that they were not damping at all before that last ride.
In any case, I now have about 3/4" of travel in the front end. Yay. The ride is a bit better, and taking bumps is much easier. The forks are still pretty stiff, but at this rate, by next year, I might have them totally broken in. I honestly might not have bought them if I had known in advance that they'd take this long to break in. Next time I get new forks, I'll follow Kim Jong illest's advice!!