Dinosaur here.

When I was coding, the most common ‘bad thing’ was to violate the stack (i.e. reach in and twiddle something outside of the current frame). We often did this for performance gains as machines were desperately slow. (FWIW we were working in assemblers and C, and later, C++, in which this sort of thing was quite possible). It made for code that was difficult to maintain and semi-impossible to port to another architecture.

I’d sometimes explain to non-computer folks that my job “was the most fun in the world — turned into occasional misery through the application of time pressure.” I’d guess that the time pressure part hasn’t changed.