As an American living in Japan, I once felt that it was my right to strike up a random conversation with a stranger. In fact, I was raised in a family where these types of conversations happened on a daily basis. My father, a salesman, often chatted with people on planes, trains, restaurants, and in any other public place.
I never felt it was awkward, though I remember expressing some degree of anxiety about his conversations with waiters and waitresses in fear of them taking something the wrong way and negatively impacting our food. Nevertheless, these kinds of random conversations took place on a regular basis, and it became second nature for me to continue in his footsteps, until I arrived in Japan.
On a Train in Japan: Keep Quiet and Carry On
Japanese public places are not really the place for random conversations. More importantly, Japanese commuters, overall, are just not in the mood to talk to strangers. One never really hears loud conversations on trains. Even conversations between friends are muted to respect the quiet environment of the train. This is something that I have come to love about Japan. The daily commute is nice and calm because the atmosphere of the train is so harmonious.
No, Really, Japanese Trains Want You to Be Quiet
The desire for calm can get a little overboard. One might see someone glaring at someone else's use of headphones on the train; even the spilled-over sounds of music from headphones can be considered a nuisance by some. It is considered a nuisance when women put on makeup on the trains, or even on the train platform, by some, though this attitude is slowly changing. Mothers with crying children often even exit the train and wait for the next train in order to avoid annoying others.
It's nice, once you get used to it
Still, this courtesy is really quite good for the average expat in Japan. Upon visiting America, I noticed a total lack of common courtesy with regard to behavior in public places. On my plane ride back, you wouldn't believe the things a man from Idaho tried to tell me. I put on my headphones to avoid him - which only made him shout louder.