Hallucinations in code are the least dangerous form of LLM mistakes

> Just because code looks good and runs without errors doesn’t mean it’s actually doing the right thing. No amount of meticulous code review—or even comprehensive automated tests—will demonstrably prove that code actually does the right thing. You have to run it yourself!

I would have stated this a bit differently: No amount of running or testing can prove the code correct. You actually have to reason through it. Running/testing is merely a sanity/spot check of your reasoning.

I’m not sure it’s possible to have the full reasoning in your head without authoring the code yourself - or, spending a comparable amount of effort to mentally rewrite it.

Spoken by someone who hasn't had to maintain Somene Else's Code on a budget.

You can't just rewrite everything to match your style. You take what's in there and adapt to the style, your personal preference doesn't matter.