Level three definitely exists, and it's useful to be able to talk about levels of correctness. That doesn't mean it's always required to be level 3 correct. Tha

Level three definitely exists, and it's useful to be able to talk about levels of correctness. That doesn't mean it's always required to be level 3 correct. That entirely depends on your risk profile. If you're doing a one-off server side maintenance tool, it may be fine. If you're doing flight control software for an airplane, it's not.