Hi,
Custom fields allows you to create this feature.
In "Display -> custom fields" you can create a new field for "product" (with column name "custom_name" for example)
Select a "text" custom field and set "no" to the Front-end display.
After that, you have to edit the product display view and change code where the product name is displayed via the menu Display->Views.
So, in your new custom field (which is hidden in the front-end) you can set a new name which could contain some HTML code.
You won't have any conflict with the rest of HikaShop system because the name of the product (without formating) will be used.
product/show.php
echo $this->element->product_name;
Becomes:
echo $this->element->custom_name;
After that, in the back-end, you could assign an HTML formatting name to your product. Name which would be used just in the product/show (or in other views if you modify it).
Regards,