If you can find the official legal interpretation that says time logged while instructing is compensation, please post a link. That is a sketchy area and I'm sure there are plenty of airline pilots who instruct their family and friends on the side. Its the same stupid concept that says you can't fly your friend's airplane for free b/c the time is compensation. I guess that could mean anyone who had their parents pay for their flight training was engaged in commercial operations since they got the flight time without paying for it out of their pockets.