Hey Richard, I knew it would be just a matter of time before we actually agreed upon something.
Even now divers are taught in different ways. For example, I never teach my students to donate the primary because it is against every rescue technique taught by every major life-saving organization worldwide i.e. never put the rescuer at risk! You know the primary works, but only can be reasonably sure that the secondary does.
Along the same vein, when buddy breathing you always keep control of your regulator. It's also important to hold it in a manner so the receiver can reach the purge button.
Although this is a bit off topic (to teach buddy breathing or not, and if so at what level) I didn't want the chance to pass by without saying something. Who knows when the opportunity will come along again that we will agree on anything...