Is that one has to say something friendly when passing one’s neighbors on the sidewalk, if one doesn’t want to offer up a tortured, tight-lipped, half-smile, and there’s only one greeting that’s 1. Easy to remember, 2. Easy to speak, 3. Natural and fluid-sounding, 4. Vaguely folksy without seeming put-on, and 5. Breezily benevolent, and that’s “Mornin,’…