Perhaps the answer is that there are multiple hierarchies of [dis]utility, for instance: n dust specks (where n is less than enough to permanently damage the eye or equate to a minimal pain unit) is hierarchy 1, a slap in the face is hierarchy 3, torture is hierarchy 50 (these numbers are just an arbitrary example) and the [dis]utility at hierarchy x+1 is infinitely worse than the [dis]utility at hierarchy x. Adding dust specks to more people won’t increase the hierarchy, but adding more dust specks to the same person eventually will.
Perhaps the answer is that there are multiple hierarchies of [dis]utility, for instance: n dust specks (where n is less than enough to permanently damage the eye or equate to a minimal pain unit) is hierarchy 1, a slap in the face is hierarchy 3, torture is hierarchy 50 (these numbers are just an arbitrary example) and the [dis]utility at hierarchy x+1 is infinitely worse than the [dis]utility at hierarchy x. Adding dust specks to more people won’t increase the hierarchy, but adding more dust specks to the same person eventually will.