Comment by zokier

> it's precisely when the industry accepted this as a law -- instead of treating it as something that needs be trained out of junior programmers -- is when software quality started to tank.

And precisely when exactly do you think that happened, when do you think there was this golden age where people actually relied on only documented behavior?

Windows and Linux both have been bending backwards to retain all sorts of undocumented features since early/mid 90s. Glibc was notoriously hampered by emacs relying on some details of its internals. C programs relying on implictly or explicitly undefined behavior has caused endless handwringing as long as there has been a C standard. The list goes on and on. Relying on implementation details has been the modus operandi in computing since day 1.