Clarify that modal dialogs escape inertness of ancestors.

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@@ -75967,9 +75967,12 @@ END:VCARD</pre>
   <var>document</var>'s <span>top layer</span>. While <var>document</var> is so blocked, every node
   that is <span>connected</span> to <var>document</var>, with the exception of the
   <var>subject</var> element and its <span>flat tree</span> descendants, must become
-  <span>inert</span>. (The elements excepted by this paragraph can additionally become
-  <span>inert</span> through other means; being part of a modal dialog does not "protect" a node
-  from being <span>inert</span>.)</p>
+  <span>inert</span>.
+
+  <p><var>subject</var> can additionally become <span>inert</span> via the
+  <code data-x="attr-inert">inert</code> attribute, but only if specified on <var>subject</var>
+  itself (i.e., <var>subject</var> escapes inertness of ancestors); <var>subject</var>'s
+  <span>flat tree</span> descendants can become <span>inert</span> in a similar fashion.
 
   <p class="note">The <code>dialog</code> element's <code
   data-x="dom-dialog-showModal">showModal()</code> method causes this mechanism to trigger, by