This is a great thread, thought provoking, with some interesting observations and opinions.
I can certainly vouch for the benefits of the Gliding Federation of Australia's emphasis on adult learning and communication, motivation and processing issues. I hope that emphasis is not lost in future - GFA is revising and updating its training and coaching system with a view to strengthening post solo development aspects. As a GFA L3 instructor, training the trainers, I find myself personally emphasising these communication, motivation, adaptive methods issues quite a bit. So I appreciate those supportive comments.
In gliding, in GA and RA I have alse experienced some very good and not so good instructors. I think one of the positive discrimination issues is that of the really good instructors constantly reinforcing high airmanship standards, good judgment and excellent lookout, and assisting in developing good situational awareness. Think about those instructors who can quietly and consistently help develop better workload management, leading to safer habits, better focus and discipline, assisted by sharp lookout and reinforcing better situational awareness, which in turn builds better judgment and higher airmanship standards. Note that the really good ones can understand the cascade, the interdependence, and use multiple instructing techniques to build that core in their students - all the while motivating them - and in turn they absorb the theory and practice much better.
So - I would argue that the very good instructors would normally be very good pilots, sometimes quite critical of their own flying - and good instructors, with the potential of being very good, would know their own shortcomings as pilots and work darned hard at improving themsleves.
There are some adept, knowledgeable, skilled pilots out there, but with poor airmanship and judgement, poor lookout, poor situational awareness, poor adaptability, poor self-awareness, or unsound risk appetite, who should not be considered "good" pilots, and who should therefore never instruct (regardless of their ego and aspirations). Others may have great airmanship, judgment, situational awareness etc, but lousy motivation and communication skills. Ditto.
Are all "good" pilots good instructors? No. But it's worth thinking about the really good ones and the discrimination factors, their standards, what they do beyond teaching, and the breadth and depth of their tool kits.
On on!