Good questions there sabro san !! Yes, I do go by that 'rule'. It is an element of intelligence that can be seen not only in humans, but, and especially in the Great Apes, in animals to some extent too. As you mentioned there sabro, it is the element of reciprocality, and
every good salesperson knows it well !!
In human and animal bonding, it is very necessary to maintain social structure, and, of course as sabro so correctly mentioned, it is not Christian nor Jewish, nor Hindu. . . it is natural.
Regarding the M person, I'd tend to agree with Sensuikan San.
One way that I apply this in my life, is by listening carefully to people when they talk. I feel that everyone wants to be heard, including me, and so I am careful to listen before giving advice, or saying anything about the matter presented to me. For that reason, my students at the Uni trust me with helping them with their problems. (usually about [in order] love, work, home-situation, study)