StackOverflow has its flaws but compared to the competition it's heaven. Moreover, when reading OP's 'Computer systems are designed to be figured out from their manuals or APIs' I stop reading. Sometimes systems are so new there isn't a manual yet (eg when Node started) or you just deal with complex matters where multiple systems are interweaved.
I learned tons of stuff on SO I would have never figured out myself. Also, how comments and answers are conceptually and visually separated is just very smart and the pain point of every other Q&A site.