Hello,
The ACL "characteristics" is needed if you want to allow your vendors create the characteristics (and the values) ; and then use them to create variants.
To create a variant of a product, you first need to add a characteristic to the (main) product, thus you need the corresponding ACL for HikaMarket (product > characteristic).
Afterwards, you can find specific ACL if you want to give different rights for the variant edition than the (main) product edition.
Once the ACL "characteristic" is given to a vendor, he will have a specific entry in his dashboard to see and edit its own characteristics and its own values.
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.