I can't speak for the other editions, Youpersup, but your presentation of what is in the 2008 handbook is in error - as is the artwork in the illustration. Earlier editions did not reference the 'flat, non-raised' parts of covers, as that is new to the 2008 code.
I say the handbook is in error, becuse the language accompanying the artwork is exactly opposite of the code section - which is printed right next to the artwork. They both can't be right.
As for thread locking, there's really nothing vague about that. I mean, "Machinery's handbook" and other shop references are replete with discussion of the various means. Since no specific method is called for by the code, I'd have to accept any method. Naturally, some of these methods cannot be identified without taking the thing apart - and such action might destroy the thread-locking mechanism.
All these semantics being tossed about, attempting to extend the code beyond what it says, remind me of the 'sheet metal screw' silliness of a few years back. I submit that if we're reduced to arguing what the meaning of 'is' is, then perhaps we have bad code, that the code has crossed over into design work - something the code explicitly states is outside its' scope.
Now, if someone has a different understanding as to what the code is referring to when it speaks of 'flat non-raised' parts of covers, I'd love to see a picture. As best I can tell, the code was written as it was so as to specifically allow the use of these covers without need for a jumper.
