Hello,
The review system in HikaShop is not made to have replies.
We have in our TODO list (with a lot of other things) a refactoring of the vote/comment system in order to make it better and more flexible.
Afterwards, there are three Joomla comment system which are integrated with HikaShop : jcomments, jomcomment and komento.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.