If I could add just slightly to this bit, it's probably important for writers to understand that many potential readers don't see the subtitle until after they've clicked on the story. If they're in full browser mode on a laptop, they'll see both the title and the subtitle before they click. Otherwise, they usually won't see the subtitle until after they've loaded the story.

To takeaways from this.

1. Using the subtitle to help potential readers understand what the story is about is not a good strategy.

2. Providing just a little bit more information to keep readers interested once they have clicked is probably a good strategy.