"I think a better title would be "A significant amount of (shipped, so-called production-quality) code is not fully understood by its authors"." Well duh. Not

"I think a better title would be "A significant amount of (shipped, so-called production-quality) code is not fully understood by its authors"." Well duh. Not a single program shipped today, no matter how small, is "fully" understood by its authors, because to do so, one would have to understand every implementation nuance and bug of OS layers, libraries used, other parts it interacts with, ... And even for less strict definitions of "fully" - for any program that took longer than say 2 weeks to write, how can anyone claim they really know the details of everything, at the same time? Including the nuanced differences between various of OS calls, and the effect some environment variable might have on your localization code, just to name one thing?