The 'rules' appear neither consistent, accessible or cross-contextual. Accessibility is the big issue from my perspective (someone who is completely baffled by 'the' rules or what they are or where to find them).
As a slight, there is a particular snide attitude that comes from people versed in a hierarchy that is quite repulsive a lot of the time. One can be informative without being patronising, condescending or rude - and there are plenty of people around who are helpful and polite/understanding (fxh comes to mind). Some people seem to act as if knowing how to dress gives them a free pass on manners, then get miffed when people discount their ideas.
You need to master the rules before you should try breaking them. Nearly every one of Mantons fits have been home runs, can we say the same about WAYWRN or this thread?
Of course when you know nothing everything can look good to you. Instead of concluding that the rules don't really matter, consider instead that it's because you know nothing.
It's a sad state of affairs.
While I am not disagreeing I have to point out that what works for some won't work for others. Manton's fits (looking back as obviously I wasn't here when he was posting consistently) are great, but they don't generalise as much as I feel you're implying. While there is, undoubtedly, plenty to learn and think about I, at least, could not dress like him without being prohibited in my job.
Perhaps this isn't the forum for people in my situation, but at least the Australian Members thread is incredibly informative and there's plenty to learn about how to compromise rather than fail across the board.
...and not to mention that one of the reasons for posting fits is to find ways of improving fits, or double checking how well one has played by 'the rules'.