Should I Report A Cocaine User?

I believe you're getting downvoted because this question isn't very relevant for the EA forum, which I think is understandable. Perhaps it would be better suited for Reddit or Twitter and maybe a quick take here. But to answer your question: I would not get involved, mostly because you don't know this person. There are so so many people doing cocaine and other drugs, reporting them doesn't really solve anything. You might ruin someone's life. You only get involved in case you know the person really well and then you just start with personally talking to them. Even then I'm not sure I'd report it. They're often a victim of their addiction, so they need help and support rather than punishment.

I guess an important question to begin with should be what chain of actions to you expect from your report. Do you want to report them to the police? The university? Do you want to show pictures as evidence or bring them to an occasion where the asserted crime happens? What then? They write a report, nothing happens except scoreched earth?

Without diving into the details of peoples motivations for doing cocaine and their actual needs, doing cocaine is a problem common enough in most western countries that reporting a single individual consumer will likely have negligible consequences at large and potentially harmful consequences for yourself. Reporting individual cocaine consuming students doesn't seem like a realistic strategy to combat drug cartels but comes with personal risks that don't seem worth it, even if you believe in some positive consequences from said report (like this guy not using cocaine anymore?), which I'd be sceptical of in the first place.