[Scott Godin]

so far every attempt I've made to replace Xlite/View/Category.php with my module's Xlite/Module/MHG/TemplateMods/View/Category.php either breaks the store forcing me to do a soft reset, or simply fails to do anything.

Not sure what I'm doing wrong. Does the documentation need updating?

I've updated the template file to use this, via theme_tweaker (though I would much rather have this edited template file as part of my module, since I'm using my module to override it!)

<div IF="isVisible()" class="category-description">{getDescription():h}</div>

and then added the following to my module (a stripped down and edited copy of Xlite\View\Category.php )

<?php
// vim: set ts=4 sw=4 sts=4 et:

/**
 * X-Cart
 *
 * NOTICE OF LICENSE
 *
 * This source file is subject to the software license agreement
 * that is bundled with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://www.x-cart.com/license-agreement.html
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to licensing@x-cart.com so we can send you a copy immediately.
 *
 * DISCLAIMER
 *
 * Do not modify this file if you wish to upgrade X-Cart to newer versions
 * in the future. If you wish to customize X-Cart for your needs please
 * refer to http://www.x-cart.com/ for more information.
 *
 * @category  X-Cart 5
 * @author    Qualiteam software Ltd <info@x-cart.com>
 * @copyright Copyright (c) 2011-2015 Qualiteam software Ltd <info@x-cart.com>. All rights reserved
 * @license   http://www.x-cart.com/license-agreement.html X-Cart 5 License Agreement
 * @link      http://www.x-cart.com/
 */

namespace XLite\Module\MHG\TemplateMods\View;

/**
 * Category widget
 *
 * @ListChild (list="center", zone="customer")
 */
class Category extends \XLite\View\AView 
{

    /**
     * Check widget visibility
     *
     * @return boolean
     */
    protected function isVisible()
    {
        
        if ( parent::isTitleVisible() && ($this->getCategory()->getMainTitle() == $this->getCategory()->getViewDescription() ) ) 
        {
            return false;
        }
        else
        {
            return parent::isVisible() && $this->getCategory()->getDescription();
        }
    }

    /**
     * Return description with postprocessing WEB LC root constant
     *
     * @return string
     */
    protected function getDescription()
    {
        return $this->getCategory()->getViewDescription();
    }
}

I have also tried doing it with

class Category extends \XLite\View\AView implements \XLite\Base\IDecorator