Address feedback on always creating a fresh traversable

This leaves some aspects implementation-defined as they are inherently UI.

notifications.bs

@@ -575,8 +575,16 @@ platform supports activation, the user agent must (unless otherwise specified) r
   <p>If <var>navigationURL</var> is non-null:
 
   <ol>
+   <li><p>If there is an existing <a for=/>top-level traversable</a> <var>traversable</var> within
+   the user agent's <a for="user agent">top-level traversable set</a> whose
+   <a for="navigable">active document</a>'s <a for=Document>URL</a> <a for=url>equals</a>
+   <var>navigationURL</var> with <a for=url/equals><i>exclude fragments</i></a> set to true, then
+   <a for=/>navigate</a> <var>traversable</var> to <var>navigationURL</var> and return. If there are
+   multiple <a for=/>top-level traversables</a> that satisfy the condition the user agent has to
+   pick one in an <a>implementation-defined</a> manner.
+   <!-- Should maybe set userInvolvement correctly here and below. -->
+
    <li><p><a>Create a fresh top-level traversable</a> given <var>navigationURL</var>.
-   <!-- Should maybe set userInvolvement correctly here, even though it doesn't do anything today. -->
 
    <li><p>Return.
   </ol>