Alejandro review

Author: sarahhaggarty

docs/topics/extensions.md

@@ -4,10 +4,9 @@ Kotlin _extensions_ let you extend a class or an interface with new functionalit
 design patterns like _Decorator_. They are useful when working with third-party libraries you can't modify 
 directly. Once created, you call these extensions as if they were members of the original class or interface.
 
-The most common forms of extensions are _extension functions_ and [_extension properties_](#extension-properties), which
-are available in [companion objects](#companion-object-extensions) as well as classes and interfaces.
+The most common forms of extensions are [_extension functions_](#extension-functions) and [_extension properties_](#extension-properties).
 
-Extensions don't modify the classes or interfaces they extend. By defining an extension, you aren't inserting new members,
+Importantly, extensions don't modify the classes or interfaces they extend. By defining an extension, you aren't inserting new members,
 only making new functions callable or new properties accessible via special syntax.
 
 ## Receivers
@@ -156,8 +155,8 @@ For more information about generics, see [generic functions](generics.md).
 ### Nullable receivers
 
 You can define extension functions with a nullable receiver type, which allows you to call them on a variable
-even if its value is null. When the receiver is `null`, `this` is also `null`. To avoid compiler errors, we recommend checking
-`this == null` check inside the function body when defining an extension with a nullable receiver.
+even if its value is null. When the receiver is `null`, `this` is also `null`. Make sure to handle nullability correctly
+within your functions. For example, use `this == null` checks inside function bodies, [safe calls `?.`](null-safety.md#safe-call-operator), or the [Elvis operator `?:`](null-safety.md#elvis-operator).
 
 In this example, you can call the `.toString()` function without checking for `null` because the check already happens inside
 the extension function: