Hi,
In HikaShop you can change the subjects of the emails. You can edit them in the Hikashop backend (System > Emails) (it requires HikaShop Business, version you have).
HIKASHOP_LIVE is a special constant which is defined depending the running website. It contains the domain name that the user use to access to the store.
It is not something you can override. But you can display another website.
The key "ORDER_STATUS_NOTIFICATION_SUBJECT" is a translation key, so you can change the translation and remove the "%s" which will be replaced by the value of "HIKASHOP_LIVE".
At this moment you can put directly the url you want.
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.