Hi,
The compare page has been developed some years ago by myself ; it was a custom development that I made and I gave the code to the HikaShop team.
The original feature request didn't require some kind of "memory" for the comparison ; so yes, the feature could be better but it will also require some extra development.
HikaShop is also an open-source project, where external developers can share their work with the rest of the community.
The improvement of the compare system is in the HikaShop TODO list, like other various tasks.
But the good point is that the compare system is very flexible and allow you to compare product by just giving the product ids.
You can create a "compare page" and specify yourself the products, like we did in our demo website :
demo.hikashop.com/index.php/en/other-features/comparison-page
That's why Nicolas told you that the feature is possible ; but even if it's not something really complicated (like managing taxes) it requires some time to make it right (with an interface flexible enough to allow customization).
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.