diff --git a/xep-0280.xml b/xep-0280.xml
index 1980f237..ad638e21 100644
--- a/xep-0280.xml
+++ b/xep-0280.xml
@@ -292,7 +292,7 @@
       <li>A &MESSAGE; of type "groupchat" SHOULD NOT be carbon-copied.</li>
       <li>A &MESSAGE; containing a &xep0249; SHOULD be carbon-copied.</li>
       <li>A &MESSAGE; containing a <link url='https://xmpp.org/extensions/xep-0045.html#invite-mediated'>Mediated Invitation</link> SHOULD be carbon-copied.</li>
-      <li>A private &MESSAGE; from a local user to a MUC participant (sent to a full JID) SHOULD be carbon-copied<note>The server SHOULD limit carbon-copying to the clients sharing a <strong>Multi-Session Nick</strong> in that MUC, and MAY inject the &lt;x/&gt; element into such carbon copies. Clients SHOULD ignore carbon-copies of MUC-PMs related to a MUC they are not joined to.</note>.</li>
+      <li>A private &MESSAGE; from a local user to a MUC participant (sent to a full JID) SHOULD be carbon-copied<note>The server SHOULD limit carbon-copying to the clients sharing a <strong>Multi-Session Nick</strong> in that MUC, and MAY inject the &lt;x/&gt; element into such carbon copies. Clients can not respond to carbon-copies of MUC-PMs related to a MUC they are not joined to. Therefore, they SHOULD either ignore such carbon copies, or provide a way for the user to join the MUC before answering.</note>.</li>
       <li>A private &MESSAGE; from a MUC participant (received from a full JID) to a local user SHOULD NOT be carbon-copied (these messages are already replicated by the MUC service to all joined client instances).</li>
     </ul>
     <p>As the above is an implementation detail of servers, clients MUST NOT rely on the server implementing a particular set of rules for which messages are eligible for Carbons delivery.</p>