The guy in the plaid lumberjack shirt wrote with a frenzy that gave evidence that he was writing either the great American novel or an angry missive to an ex. I'm betting on the novel-- the lumberjack shirt in the heart of a large city spoke of irony. Writing in a coffee shop is always, for me, an exercise in character development. I've already got a place for Mr. Plaid Shirt in my own great American novel --as a jilted lover writing an angry missive to his ex. In that scene I will have him quaff the remains of his now-cold coffee and proceed to his dentist's office where he will sit in the waiting room with notebook on his lap and face writer's block as he tries to work into his story the man in the denim shirt at the coffee shop.