Hi,
Yes indeed, I was only talking about the vote, not the comments.
I think that the easiest solution will finally to do a custom plugin, not plugged on the mass actions.
And this plugin will be based on the function "onBeforeVoteCreate()" and/or "onBeforeVoteUpdate()".
So, there you have the whole element, the vote rating, the id of the product and the comment based on the vote type.
When this trigger is called, you can do a check on the categories of the product, get the other products of the same category and add the desired entries in the #__hikashop_vote table directly, and update the columns "product_average_score" and "product_total_vote" in the #__hikashop_product tables of the desired products.
That way the comments will be added to the other products of the same category, and the vote ratings updated.
Hope this make sense