Add text from explainer around privacy concerns

source

@@ -22854,7 +22854,14 @@ document.body.appendChild(wbr);</code></pre>
   <code>a</code> elements that create <span data-x="hyperlink">hyperlinks</span>, if present,
   provides the desired translation language of the linked resource. The value must be a valid BCP 47
   language tag. <ref spec=BCP47> When navigating the anchor, user agents that support client side
-  translation should display the page in the desired language.</p>
+  translation should ask the user if they wish to translate to the desired language. Since the page
+  may contain sensitive data user agents should have a confirmation prompt to the user before
+  performing the translation. The user agent should not automatically translate an anchor with
+  hrefTranslate set based solely on that the user has previously translated to the target language.
+  If the user agent wishes to support automatic translation it must use additional data such as a
+  set of trusted URIs to which translations are allowed by the user. If the user has automatically
+  translated the page based on a previous confirmation from the user it should make it clear to
+  the user that page was machine translated.</p>
 
   <div class="example"> <p>The following example shows how you can specify different <code
   data-x="attr-hyperlink-hreflang">hreflang</code> and <code