Currently in my templates, parts of items-slider.phtml as following:

<?php if($this->helper('catalog/product_compare')->getAddUrl($_product)): ?>
    <li><a title="<?php echo $this->__('Add to Compare') ?>" href="<?php echo $this->helper('catalog/product_compare')->getAddUrl($_product) ?>" class="link-compare" data-toggle="tooltip" data-placement="top" data-original-title="<?php echo $this->__('Add to Compare') ?>"><?php // echo $this->__('Add to Compare') ?></a></li>
<?php endif; ?>

I think this could be the reason, because it will return with a link which with a encoded url which is the Ajax call, in fact it should be the Homepage link in this case.