Sometimes I learn a good bit from the "Similar Topics" beneath my original post.
This time, I think I learned that (unwittingly), I broke an 11th commandment:
"Thall shalt not use products for their unintended/non-approved use, especially in the garden, even if it's perfectly harmless".
So, I'm left with a dilemma. I have accidentally made (or might accidentally make in the near future) a solution of a half teaspoon of washing-up liquid to a liter of cold water. Having accidentally made such a solution, I will NOT use it for insect control. That might be a violation of the law (I'm not sure what the extradition laws are regarding serious crimes of this type, i.e., illegal use of washing up liquid).
I will re-purpose the water, carefully applying it to some lettuce with some small black dots on the leaves (very tricky dots - some of them move occasionally). The water will be applied as a cleaning agent to remove the dots, and possibly as a sticking agent for a foliar feed of the essential plant nutrient, dihydrogen monoxide (I've been advised that lettuce can't survive without this nutrient).
I will see if the cleaning agent works to get rid of the black dots. If it doesn't get rid of the dots, I might accidentally make a stronger solution.
Let me know if I stuck the landing on this one.