Speaking of the headcloth, what you said reminded me a bit of José Morelos, a Mexican priest and leader and martyr in Mexico's war of independence against Spain, depicted on the "barely silver" Mexican 1 Peso:
https://en.numista.com/catalogue/pieces3550.html
According to his biography he wore a similar headband like Tubman's, visible on the coin, to relieve migraines.
Anyway, when you say:
"At least one other person is depicted on notes wearing headcloths for the same reason. And others are shown wearing headcloths for their own sake. Who?"
Do you mean notes from any particular country?