[Tim Ingmire]

OK, Andy NYE wrote (and I quote) - A Dive Marshall would NEVER pair off a air and nitrox diver together

Thats fairly absolute stuff.

Andy Wetlettuce then writes  
"How can Andy be possibly 'Wrong'." quickly followed by "There is also no reason why a nitrox diver cannot dive with an air diver if they both plan the dive and dive the plan and both divers plan accordingly.".

So, Andy you've answered your own question - and it seems we agree.

I don't care what Andy Nye chooses to do but he wasn't saying anything about what he chooses to do - by laying down a 'law' like this is the kind of BS that turns people off BSAC - its not even a position that the BSAC take.

Yes there are good reasons for not pairing a Nitrox and Air divers in some circumstance but certainly not all.  That's what makes a good DM, knowing the right decisions to make in a given situation, not blindly following some made up rule - we agree again.

Oh, and where did I say that I wouldn't consider a buddy pair's gasses?

I would imagine that the log sheet thing is just one of simplicity and convenience and actually reflects nothing much in particular.  There's nothing to say that buddy pairs have to be logged on the same sheet.