Hi,
Canonical URL is for search engines. Even if a page is "duplicated", the canonical url will notice the search engine which page should be referenced. There is no redirection or other thing. It's just for the SEO
Redirection is not a good solution because you can loose information (like the breadcrumb, or else).
For the user it's not something problematic to have "duplicate" url (which are not really duplicate).
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.