oh definitely not a stranger, but a dive buddy, someone you know.To a complete stranger? Not a chance.
There is usually no debriefing after the dive unless something has gone wrong. For some divers and myself that could be the last dive of the trip.
I have been asked on several occasions by the fellow divers of my set up(BP/W with long hose) in rec dive.
And some of my insta-buddy did not like the idea of primary donation.
Giving advice on any improvements is typically not well received which is why I just keep my mouth shut. Though I do sometimes ask others about my trim. "Did I break at the waist?" "What angle was my body?" That's about it.