Describe behaviour of down-arrow when editing text

Fixes #970

index.html

@@ -193,7 +193,7 @@ chown -R <strong>username</strong>:<strong>username</strong> ~<strong>username</
                 <li><kbd>ALT-g</kbd>: Focus on buffer list filter</li>
                 <li><kbd>ALT-h</kbd>: Clear unread counters in every buffer (locally)</li>
                 <li><kbd>Esc-Esc</kbd>: Disconnect (double-tap)</li>
-                <li>Arrow keys: Navigate history, or navigate quick search buffer results.</li>
+                <li>Arrow keys: Navigate history, or navigate quick search buffer results. Pressing <kbd>↓</kbd> while writing a message pushes it onto the history for later re-use, without sending it.</li>
                 <li><kbd>Tab</kbd>: Complete nick</li>
                 <li>The following readline/emacs style keybindings can be enabled with a setting: <span title="Move cursor to beginning of line"><kbd>Ctrl-a</kbd></span>, <span title="Move cursor to te end of the line"><kbd>Ctrl-e</kbd></span>, <span title="Delete from cursor to beginning of the line"><kbd>Ctrl-u</kbd></span>, <span title="Delete from cursor to the end of the line"><kbd>Ctrl-k</kbd></span>, <span title="Delete from cursor to previous space"><kbd>Ctrl-w</kbd></span></li>
               </ul>