Thank you Bob, going through this string was a little painful but was interesting. He speaks for me as well but I'd like to add that many divers have physical limitations however the ones that are up front with them, that plan for the emergency that hopefully will never happen, and communicate that to their buddy is a thoughtful diver, one that I would trust. The diver I trust most has asthma, carries an inhaler in her BCD and always talks to the captain of whatever boat we're on prior top diving. As for the original question, I believe it's been answered. If it's an immediate threat then you can voice concern, in fact it's your moral responsibility. If it's not then I'd do what you are doing, talking with other divers then talking with the person you are concerned with in a non-confrontational manner. I admire that fact you care enough to talk about it and suspect you'll make the right decision.