not much different than sitting for dinner with friends and pulling out your cell phone and being absorbed in chatting.
some older people entering a room feel its proper to address others int he room,at least eye contact or a nod and a smile.. Ive noticed some younger people don't think that way. In other words what is considered polite is changing with the times.
probably one that may resonate with elders is leaving a dinner table mid meal, some would feel it polite to ask to be excused or excuse themselves, lets say they went away min meal , to take a phone call.
even though they are not a child, they are recognizing the interruption and the people near them.
a younger person may not even think of that at all.
I find the sound of someone else listening to headphones irritating and somewhat rude. you have a situation where the two of you are listening to the same music but only one of you can really hear it very well. not everyone would find that irritating. some might depend upon what you are used to. some will do that to intentionally block their attention from others so they are basically zoning them out
to focus upon some other thing like music or conversation.
some hold a door for the next person others let it go and let them go grab the handle. I'm not trying to insult anyone but its somewhat cultural, people who live prior , in close proximity to many others tend to focus on themselves and people who live in a small town environment are more used to a different way of politeness.
if a headset bugs you you have every right to say so. If it does not, then its a non issue.
if the person is consulting about game play, well its basically the same as having an instructor follow you, that may be fine for a learner maybe less so for a serious game environment. I doubt they allow that in poker either.
a lot of the game is strategy so maybe some depend if they are using it in a way that is strategic, a pro can read a table better than an amateur even from quite a distance.
if two mid level players are playing and one has a pro helping on his headset there is an obvious disadvantage, if your personal music choice or conversation is offensive to someone else, that's rude if you are aware of it and still continue. doing things to bug someone to create an advantage intentionally is sharking.
Many will walk away if they are subject to such ,past a level of toleration. some will suck it up, depends on the circumstances.
everyone doesn't; normally leave the room because they dont like the song on the radio station but if its a continuous thing, its polite to allow others to have some say in music choices , thus including them and coming to agreement. with a headset the music is the persons choice but if others hear it , they are sharing their music. Like with dropping a door in someones face, it is somewhat to do with what a person views as normal or acceptable. some would see that as normal while others feel the person is being rude.