Add note about how changes are determined

content/docs/context.md

@@ -64,7 +64,7 @@ Accepts a `value` prop to be passed to Consumers that are descendants of this Pr
 
 A React component that subscribes to context changes.
 
-Requires a [function as a child](/docs/render-props.html#using-props-other-than-render). This function receives the current context value and returns a React node. It will be called whenever the Provider's value is updated.
+Requires a [function as a child](/docs/render-props.html#using-props-other-than-render). The function receives the current context value and returns a React node. All consumers are re-rendered whenever the Provider value changes. Changes are determined by comparing the new and old values using [`Object.is`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is).
 
 > Note:
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