Hi,
The WYSIWYG custom field display his content directly.
There is some kind of trigger in Joomla to "prepare the content" ; that feature is used in Joomla article and some other places.
In HikaShop, the product description is display with that trigger. It allow the Joomla "content" plugin to modify the data before the display.
But the WYSIWYG custom field do not use that trigger because it display directly the content.
It means that you have to edit the administrator/components/com_hikashop/classes/field.php and modfy the "show" function in the class "hikashopWysiwyg" :
function show(&$field,$value) {
return JHTML::_('content.prepare', $this->trans($value));
}
Otherwise, I'll submit your feature request to the rest of the HikaShop team to see if we add it directly in HikaShop or if we create an option for it.
Regards,