Correct description of __proto__ initializer and distinct it from the accessors

files/en-us/web/javascript/reference/global_objects/object/proto/index.md

@@ -21,7 +21,7 @@ The `__proto__` property of {{JSxRef("Object.prototype")}} is an accessor proper
 
 The use of `__proto__` is controversial and discouraged. It was never originally included in the ECMAScript language spec, but modern browsers implemented it anyway. Only recently was the `__proto__` property standardized by the ECMAScript 2015 specification for compatibility with web browsers, so it will be supported into the future. It is deprecated in favor of {{JSxRef("Object.getPrototypeOf")}}/{{JSxRef("Reflect.getPrototypeOf")}} and {{JSxRef("Object.setPrototypeOf")}}/{{JSxRef("Reflect.setPrototypeOf")}} (though still, setting the `[[Prototype]]` of an object is a slow operation that should be avoided if performance is a concern).
 
-The `__proto__` property can also be used in an object literal definition to set the object `[[Prototype]]` on creation, as an alternative to {{JSxRef("Object.create()")}}. See: [object initializer / literal syntax](/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer).
+The `__proto__` property can also be used in an object literal definition to set the object `[[Prototype]]` on creation, as an alternative to {{JSxRef("Object.create()")}}. See: [object initializer / literal syntax](/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer). This syntax is **standard and optimized**, and is not the same concept as `Object.prototype.__proto__`.
 
 ## Description
 
@@ -91,13 +91,9 @@ fn.prototype.myname = function () {
     console.log('myname');
 };
 
-var obj = {
-    __proto__: fn.prototype
-};
-
+var obj = {};
+obj.__proto__ = fn.prototype;
 obj.myname(); // myname
-
-
 ```
 
 ## Specifications

files/en-us/web/javascript/reference/operators/object_initializer/index.md

@@ -259,9 +259,9 @@ let mergedObj = { ...obj1, ...obj2 }
 
 > **Warning:** Note that {{jsxref("Object.assign()")}} triggers [setters](/en-US/docs/Web/JavaScript/Reference/Functions/set), whereas the spread operator doesn't!
 
-### Prototype mutation
+### Prototype setter
 
-A property definition of the form `__proto__: value` or `"__proto__": value` does not create a property with the name `__proto__`.  Instead, if the provided value is an object or [`null`](/en-US/docs/Web/JavaScript/Reference/Global_Objects/null), it changes the `[[Prototype]]` of the created object to that value.  (If the value is not an object or `null`, the object is not changed.)
+A property definition of the form `__proto__: value` or `"__proto__": value` does not create a property with the name `__proto__`.  Instead, if the provided value is an object or [`null`](/en-US/docs/Web/JavaScript/Reference/Global_Objects/null), it points the `[[Prototype]]` of the created object to that value.  (If the value is not an object or `null`, the object is not changed.)
 
 ```js
 let obj1 = {}
@@ -279,9 +279,9 @@ assert(Object.getPrototypeOf(obj4) === Object.prototype)
 assert(!obj4.hasOwnProperty('__proto__'))
 ```
 
-Only a single prototype mutation is permitted in an object literal. Multiple prototype mutations are a syntax error.
+Only a single prototype setter is permitted in an object literal. Multiple prototype setters are a syntax error.
 
-Property definitions that do not use "colon" notation are not prototype mutations. They are property definitions that behave identically to similar definitions using any other name.
+Property definitions that do not use "colon" notation are not prototype setters. They are property definitions that behave identically to similar definitions using any other name.
 
 ```js
 let __proto__ = 'variable'
@@ -298,6 +298,8 @@ let obj3 = {['__prot' + 'o__']: 17}
 assert(obj3.__proto__ === 17)
 ```
 
+Note that the `__proto__` key is standardized syntax, in contrast to the non-standard and non-performant {{jsxref("Object/proto", "Object.prototype.__proto__")}} accessors. It sets the `[[Prototype]]` during object creation, similar to {{jsxref("Object.create")}} — instead of mutating the prototype chain.
+
 ## Specifications
 
 {{Specifications}}