12 characteristics of film noir

I recently joined the social-media Q&A site, Quora.
This adds to my list of sites where I am a member but I don't really know what the site is all about.
It's like I am in the middle of a film noir and I know I will leave the cinema without having figured it out. Luckily Film Noir is one of the topics they ask questions on and that is a topic I do know lots about. Here is one of my answers:

Eddie coils to strike in noir

ONE name won’t spring to the lips of critics naming the most accomplished classic noir actors. As you may recall, classic noir usually refers to stylised Hollywood crime films made from the early 1940s to the late 1950s. Robert Mitchum who is universally recognised as an essential noir anti-hero, or maybe ant-hero, responded to the exotic title of film noir in laconic noirish fashion. “We used to call them B-pictures,” he said.

       Humphrey Bogart is the other icon of male leads in noir acting. After this duo, the picture gets a little fuzzy with the names Sterling Hayden and Dick Powell likely to rise from the mist. Maybe Kirk Douglas. James Cagney, George Raft and Edward G. Robinson if you want to stretch it to the gangster guys. No Edmond O’Brien.

       Oh, yair, Edmond O’Brien. Eddie O’Brien. Forgot about him. O’Brien starred in maybe a dozen or more noirs, including four of the most famous, The Killers (1946) White Heat (1949) The Hitch Hiker (1953) and the movie we will enjoy later D.O.A. (1950). He also played Winston Smith in the first cinematic adaptation of George Orwell’s novel 1984.