I've never diverted meds away from a patient. Honestly, it's probably crossed my mind twice in over 10 years, but both times I felt dirty and now I have some aversion to it. I've had friends lose their nursing licenses for diverting meds. So I'm not sure if it's morals, ethics, or just scared as shit that the only way I have to support my family could be gone for a lousy pill, but for some that's just not my thing.
As for the first part, junkies become nurses just like non-junkies become nurses. The lectures are the same, the tests are the same, the NCLEX is the same, all the requirements are the same.
It's safe for the patients as long as the nurse is a good nurse, but this again goes for junkies and non-junkies. What isn't safe for the patient is when an impaired nurse is taking care of them, or when a non-impaired incompetent nurse is taking care of them.
Personally, I work in a visible role, meaning there are always doctors and other nurses around 100% of the time. This is just the nature of where I work. When nurses are clinically weak and we feel patients aren't safe, it's generally seen by everyone. There is almost always a consensus amongst the other nurses and doctors, and they don't make it. I've worked in this role coming up on 5 years, if there was a discrepancy for me personally, it would've been addressed by now.
Beyond this, I will simply say that me being a junkie is simply for online entertainment