(I'm going to try and write some shorter posts while thinking through things for myself, let's see how it goes)
There is a school of thought that says you should understand the contract for any API you are programming against and only write code that stays within that contract. This is exemplified by some of the commenters on oldnewthing, by 'the right thing', by modern compilers' aggressive optimization in the face of undefined behaviour, by Design-by-contract, by static typing and by our dear linters, static checkers and valgrinds.
Then there is another school of thought that you should (just) test your code and if the tests pass it's good. This is exemplified by Linus and oldnewthing themselves, by Worse-is-better, by HTML and it's compatibility modes, by KISS and refactoring, by dynamic typing and by all our testing frameworks, red-green-refactor -tools, browserstacks and manual QA.
I think this a bit like Yegge's liberal vs. conservative - I feel conflicted about this dichotomy. I definitely want to have tests for my code and my colleagues' code, I'm writing more dynamically typed code than statically typed but I love my linting and valgrind and understanding the APIs I program to.
I think I want to prefer writing to contracts but my behaviour doesn't match.