Clarify discouragement of document.write() applies to writeln()

Author: caugner

source

@@ -116047,6 +116047,10 @@ document.body.appendChild(frame)</code></pre>
     character. If necessary, calls the <code data-x="dom-document-open">open()</code> method
     implicitly first.</p>
 
+    <p class="warning">This method has very idiosyncratic behavior. <strong>Use of this
+    method is strongly discouraged, for the same reasons as <code
+    data-x="dom-document-write">document.write()</code>.</strong></p>
+
     <p>Throws an <span>"<code>InvalidStateError</code>"</span> <code>DOMException</code> when
     invoked on <span>XML documents</span>.</p>