Maybe there should also be a protocol to punish TMOs who get straight forward decisions wrong. I know referees sometimes get it wrong as things happen in real time. But when you have super slowmo HD replays from different angles and still get a decision wrong, somebody needs to be punished. For example, Kerevi's 2nd try for the Reds against the Sharks today was an obvious double movement but the TMO still saw no reason to not allow the try.
The demise of the Springboks lie squarely on the shoulders of World Rugby and all unions who are part of the organisation. In the 70's and 80's every man and his dog protested Springbok matches as players were selected based on the color of their skins because of political interference. The same has been happening for the last 20 odd years, starting off slowly but gradually building up to where we are now. And this isn't even the end. 50% of the RWC squad in 2019 has to be non-white. »
With regards to 'a body part'. When a player runs with the ball and inexplicably loses control of the ball, it hits his knee and touches another player or the ground before he can regather it it will be blown up as a knock on. Which would then be the same as a non-kick with the heel. On the other hand, as you say, if a teammate passes the ball to you and it comes off your knee, chest or head it would be play on.