What if you buddy does not have a octo?- what if your buddy has one, but you don't know if it works? Have you practiced buddy breathing with this "buddy"?
I know I said I wouldn't comment on solo diving or post in this thread, but since you referenced my post directly I owe you a response.
1. If a diver does not have an octo, I will not dive with them as my buddy.
2. I'll know it works because my buddies equipment is my equipment. All equipment is a team resource and should be checked before the dive.
3. If I do not know the capabilities of a diver then I will not be in an extreme situation with them. One of the great things about buddies is that they are my buddy and I know and trust them. They are not random people on a boat or at a distant locale. If I'm diving on a vacation I'll go with a friend, someone from that location I've met before, or someone that is trained the same way I am.