I'm all for a good chit chat on the train, lord knows I like to engage with my customers in the 10-20 seconds it takes me to pour their tea, sort out the accessories (serviette, stirrer, milk, sugar, lid etc)....
Conversation shouldn't be stifled or frowned upon. There should, in my opinion, be no expectation of complete quiet on a train. It's not a library, it's a method of transport. Commuters, travellers and holidaymakers shouldn't be sat in stony silence like rows of naughty schoolchildren for 4 and a half hours. Talk to your tablemate, your seatmate, yeah fine but I agree, don't shout to the carriage. The only words that should be shouted in a carriage are "Tickets please" and "Teas...coffees....crisps..chocolate...sandwiches....".
My pet peeve? People who are too busy to pause a conversation on a mobile phone when asking for something, and then proceeding to use a flurry of mouthed words and hand signals to answer my queries of milk and sugar.