About fragment/Div

“A common pattern in React is for a component to return multiple elements. Fragments let you group a list of children without adding extra nodes to the DOM.”— React Docs

16 explanation

Why? Regular HTML attributes also typically use double quotes instead of single, so JSX attributes mirror this convention.
- Airbnb docs

Link: https://github.com/airbnb/javascript/tree/master/react

20 Explanation

Why? Underscore prefixes are sometimes used as a convention in other languages to denote privacy. But, unlike those languages, there is no native support for privacy in JavaScript, everything is public. Regardless of your intentions, adding underscore prefixes to your properties does not actually make them private, and any property (underscore-prefixed or not) should be treated as being public.

-Airbnb Docs