So, all y'all got me thinking.
Pretty much everything I know about the AR-15 type of weapon comes from the military. I was an infantryman. I think I'd be fairly typical of anyone who paid attention, practiced and remembers.
I know safety. I don't have any kind of certification, but someone could do a lot worse than following my instructions on the subject. It's the first thing I go over with a new shooter (or observe about someone I don't know) and I incorporate it into all things.
I know how to operate the weapon mechanically. I was taught these tasks, trained on how to do them and did them - over and over again. Again, I don't have any kind of certification, but if someone does what I tell them, it's going to be fine.
I can field strip, reassemble, inspect and pull user level maintenance on the weapon. I'm not a gun smith. If you want to take the barrel off of the upper receiver, you won't get any advice from me.
I can zero the weapon and fire it to good effect on a range or in the field under a variety of conditions. I can get someone started on the basics. But I'm not a marksmanship instructor.
That's my opinion on my opinion.