Pretty interesting : The highest score I've been able to find right now, apart from the extreme examples, is 49.6% success, 5.3% flag ... with the title "Predicting Hacker News article success with neural networks and TensorFlow".

Did the author chose that title on purpose? :)

It's fun to try a title, and then add "Ask HN:" or "Show HN:" in front of it and see the probability change dramatically, or remove the (YC ...) from the extreme examples and see the prediction change.