I agree, I don't need, or want, to say "hi" to a whole bunch of flowback jumpseaters sitting in the cabin.

My company's policy is that IF a jumpseater is actually assigned and will actually occupy the cockpit jumpseat, I need to check credentials and he/she needs to ask permission. But if they are flowing back and are assigned a passenger seat I do not even need to see them, nor do I care to. But a flowback is still considered a jumpseater and rules such as no drinking apply.

Having said that, I don't expect other airline pilots to know my company policy, so I don't mind if they stop by the cockpit to introduce themselves, even though it's an unneeded distraction. If in doubt just pop your head in the cockpit and politely ask if you need to show your credentials even though you are sitting in the cabin.