Here is a workaround for 1.16.2 file: support/include/staff/ticket-view.inc.php starting at line 1044:
Add a <br> after the input line.
No idea why it works or if this is the best workaround, but it works for me 😉
<input type="hidden" name="draft_id" value=""/>
<br>
<textarea name="response" id="response" cols="50"
data-signature-field="signature" data-dept-id="<?php echo $dept->getId(); ?>"
data-signature="<?php
echo Format::htmlchars(Format::viewableImages($signature)); ?>"
placeholder="<?php echo __(
'Start writing your response here. Use canned responses from the drop-down above'
); ?>"
rows="9" wrap="soft"
class="<?php if ($cfg->isRichTextEnabled()) echo 'richtext';
?> draft draft-delete fullscreen" <?php
list($draft, $attrs) = Draft::getDraftAndDataAttrs('ticket.response', $ticket->getId(), $info['response']);
echo $attrs; ?>><?php echo ThreadEntryBody::clean($_POST ? $info['response'] : $draft);
?></textarea>
