The book 'Moving Towards Stillness' has the author describing his experience in learning a particularly difficult kata. This one had him jump and turn in mid air in one sequence. He practiced and practiced it perhaps for a year or so and still he could not do it well, until one fine day, the Sensei told him to shift his weight in a particular manner. Suddenly, he found himself being able to do it with ease and 'mastery'.
He of course went back grumbling that the Sensei could have saved him all that effort if he only he was told that 'trick'. To which his wife responded, yes... but would you have listened to him then?
The 'listen' here is not just hearing what the Sensei has to say. We all hear things but seldom listen, because we don't understand what is being said or we are not yet in a situation that can bring about that understanding. So although, the rights and wrongs of teaching of fellow students on the mat is as much as a puzzle for me, I believe that teaching through words must come at the proper time, location and source. What would have made an excellant groundbreaking essay 10 years ago might be a complete utter nonsense today.