.....nor can the behavior of the end user who might attempt to modify the charger by splicing on a different connector.

Why did you look at me when you typed that? Sometimes I just cut off the connector and solder the leads to a board directly

 

OK, now, going through the posts again, I see that the TS has shown a picture of the connector, which is a "MAC" style connector.
The simple and totally effective means of preventing all possibilities of shock is to not power the charger until after all of the touching and cleaning are completed. THEN power the charger and hold the insulated portion of the connector and connect it to the phone.

 

Years ago I kept getting complaints from a church band that there had to be a serious short circuit in the amplifier system because they were getting terrible shocks off of the microphones.. But they were on a dry wood platform above a dry wood floor with nothing conductive nearby. And they were on a nice nylon carpet.
I suggested that it might be static electricity, and that for one practice session they should try it with their shoes off, in stocking feet. The leader told me that I was stupid and would not consider doing that, because it clearly was a power short circuit to the microphones. So I got several automotive jumper cables and grounded all the microphone stands to the steam heating pipes 15 feet away from the platform. Their shocks were worse then.
The solution was when they were not around I used some anti-static spray on the carpet. That fixed the problem until they had the carpet cleaned because it did not slide right as they moved around..