Hi,
HikaShop has an integration with Komento. It can be activated with the "Enable comments on products" setting under the Display tab of the HikaShop configuration. Did you activate this feature ?
If so, HikaShop basically just run this code on the product page:
echo KT::commentify('com_hikashop', $this->product, array('params' => ''));
which is code from Kometo.
So supposing you use this integration, the problem is in the Komento component and you'll have to check with their support.
If you use something else, then I don't know what you're using and it doesn't come from us.