So my question, "Is it too much to ask that a buddy, who starts to experience out-of-air problems, bangs on his/her tank or somehow gets my attention, and then requests my octopus?" Or, must we all learn to comply with this "new standard" which is starting to become well-known, that all technical divers donate their long primary and that it's "acceptable" to just grab it?
1) If I'm diving with you, then we've already gone over air sharing situations in the pre-dive briefing.
2) I monitor my gas supply closely, even more so as it diminishes. I always have a pretty good idea how much gas I have at any given moment without looking. I communicate this with my buddies as well.
3) I know where my alternate air sources are and am practiced in deploying them.
4) Taking all of that in mind, I don't expect you to run out/low on air.
But if you do, and you feel it's a matter of life or death for you to grab the reg I'm breathing without signaling, then by all means do so. My backup works and I'm not afraid to use it! We'll sort any other problems out once everyone has air again and we'll talk about what happened to cause you to have to just grab it without signalling once we get back to the surface.