HFD
As I said, it is not always the letter of the regulation, it is the justification in a court of law as a reasonable. Talking to my friend the expert witness there have been many cases where it was clear that no regulation banned what was being done in so many words, but the case hung on either whether the actions could be justified in accordance with normal or reasonable aviation practices. You risk the flight looking awfully like a charter with no AOC.
This I think should be clarified, as I could see certain less reputable organisations using any loophole, and putting pressure on instructors to fly, in effect, charter flights.
The source of the other information was, as stated, a retired CAA examiner.