Honestly, I think the issue you debate is clarified by the fact that there was a patient/provider relationship with an actual chart, assessment, testing, and treatment plan documented.
In Florida, even physicians are held to the standard that they must have the above on patient's to show a traceable pattern of care to substantiate the prescription.
It has always been frowned upon to treat family members surely as far back as I can remember. But I think this was instituted more as a means of ethics and personal conflict than as a means to restrict care. I am sure in a case such as "Wisconsin" states, that the criteria was met and the treatment was appropriate in that case.
The issue would seem to me to be more concern over integrity and professionalism. Personally, I would pass the care to another provider I worked with, if an option, or make sure I documented the reason I was the provider (unavailability, etc) to make sure no claims of malfeasance could be raised. Do I think the person who treated the nail injury wrong...no...not in the case as it was presented.
The key is to have documentation. If one holds every patient to the same standard of care, treating all the patients in the same manner, with the same forms of documentation, then this is something different than a prescription given due to a friendly phone call and no patient relationship. One needs to understand the rules of their state, practice under the guidelines as they state, and realize that the rules were put there for a reason. Sometimes rules are good things, meant to protect and prevent harm. If they are bad things, then work with legislation to get them changed.
I cannot think of a reason to ever treat myself, nor would I want too. I over analyze too much and being an old ER nurse, blow off more than I should. I am too close to myself to make a rational, unbiased opinion. I might know exactly what is wrong with me, but I want someone else to tell me what it is, in case I am missing something. Two heads are better than one.