Without now attacking someone personally or calling out names- wise words Neil! :thumbup:
Too many things have to be learnt of course- first technically- by earning the knowledge first hand-- just reading "someone s opinion"- and trying to transfer this stuff *as given* to someone can be dangerous. too many aspects have effect if we are talking about about especially about the dominant eye. I think i know for sure something about it (also because i m almost "one eyed" like Niels)- but i m very careful to work with a student "too fast" on a dominant eye problem. To find out his real problem (does he really has an eye problem? Just head in wrong position? Is he doing this for decades (that s the worst case- sometimes never to correct)- )
To find a solution to bring someone hittin vertical axis in the case he s not hitting the vertical axis after a long times....can be a pure pain in the ass....FOR THE STUDENT. In such a case (just one example of many what it could be) the brain is so used to do it...by thinkin he s hittin it dead center- believe me, it s sometimes almost undoable.
i drifted of a bit-sorry- i m totally with you Neil. By trying to fix a problem about the dominant eye you have to be really really knowledged- and everyone who calls himself an instructor, teacher, or whatever....will tell the student, that if he would really decide to fix this- ...that it s not sure, if he could ever make it there.
Teach what you know- learn what you don t- that s it 
This requires having an open mind!
have a smooth stroke everyone.
best wishes from overseas.