Here are the key quotes:
"“I’m not talking about cellphone conversations,” he said, “I’m talking about your typing, which really is very loud and disruptive.”
I was at a loss. I learned to write on a typewriter, and apparently I still strike the keyboard of my laptop with obsolete force. “Well,” I said, trying to figure out which of us, if either, was the jerk here, “I don’t think I’m going to stop typing. I’m a writer; I sit in here so I can work.”
He was polite but implacable. “If you won’t stop, I’ll have to talk to the conductor,” he said.
Looking around, I saw that the Quiet Car wasn’t crowded; there were plenty of empty seats. “I’m not going to leave the Quiet Car,” I told him, “but since it’s bothering you, I will move to another seat.” He thanked me very courteously, as did the woman in front of me. “It really was quite loud,” she whispered.
When the train came to my stop I had to walk by his seat again on my way out. “Glad we could come to a peaceful coexistence,” I said as I passed. He raised a finger to stay me a moment. “There are no conflicts of interest,” he pronounced, “between rational men.” This sounded like a questionable proposition to me, but I appreciated the conciliatory gesture. The quote turns out to be from Ayn Rand. I told you we talked like this in the Quiet Car."