doc: various small revisions in url

PR-URL: #14478
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

doc/api/url.md

@@ -77,11 +77,18 @@ const myURL =
 added: v7.0.0
 -->
 
-*Note*: Using the `delete` keyword on `URL` objects (e.g.
-`delete myURL.protocol`, `delete myURL.pathname`, etc) has no effect but will
-still return `true`.
-
 ### Class: URL
+
+Browser-compatible `URL` class, implemented by following the WHATWG URL
+Standard. [Examples of parsed URLs][] may be found in the Standard itself.
+
+*Note*: In accordance with browser conventions, all properties of `URL` objects
+are implemented as getters and setters on the class prototype, rather than as
+data properties on the object itself. Thus, unlike [legacy urlObject][]s, using
+the `delete` keyword on any properties of `URL` objects (e.g. `delete
+myURL.protocol`, `delete myURL.pathname`, etc) has no effect but will still
+return `true`.
+
 #### Constructor: new URL(input[, base])
 
 * `input` {string} The input URL to parse
@@ -116,7 +123,8 @@ const myURL = new URL('https://你好你好');
 // https://xn--6qqa088eba/
 ```
 
-Additional [examples of parsed URLs][] may be found in the WHATWG URL Standard.
+*Note*: This feature is only available if the `node` executable was compiled
+with [ICU][] enabled. If not, the domain names are passed through unchanged.
 
 #### url.hash
 
@@ -1142,9 +1150,11 @@ console.log(myURL.origin);
 [`url.toString()`]: #url_url_tostring
 [`urlSearchParams.entries()`]: #url_urlsearchparams_entries
 [`urlSearchParams@@iterator()`]: #url_urlsearchparams_iterator
+[ICU]: intl.html#intl_options_for_building_node_js
 [Punycode]: https://tools.ietf.org/html/rfc5891#section-4.4
 [WHATWG URL Standard]: https://url.spec.whatwg.org/
 [WHATWG URL]: #url_the_whatwg_url_api
 [examples of parsed URLs]: https://url.spec.whatwg.org/#example-url-parsing
+[legacy urlObject]: #url_legacy_urlobject
 [percent-encoded]: #whatwg-percent-encoding
 [stable sorting algorithm]: https://en.wikipedia.org/wiki/Sorting_algorithm#Stability