I have the same problem.
It looks like the problem is caused by the template override,
…/ja_portfolio/html/com_content/article/default.php
If you disavle the override (rename com_content in the template), it is possible to hide the title.
Funny is that the code that checks and displays the page title is identical in the original and the override file.
<div class="item-page<?php echo $params->get('pageclass_sfx')?>">
<?php if ($this->params->get('show_page_heading', 1)) : ?>
<h1 class="componentheading">
<?php echo $this->escape($this->params->get('page_heading')); ?>
</h1>
<?php endif; ?>
However, it is unlikely that this is a solution as it probably causes other problems.
It is just a point of direction.
//Sune