This topic goes to the very heart of ARF's existence. Our focus is the Amazon and AliExpress marketplaces, but the issues are probably the same for any kind of user-posted review on any website.
So do Amazon and AliExpress own the copyrights to product reviews? Emphatically No!
Why would they want ownership? If they have ownership, then they are responsible for the content and that would create unwanted legal liabilities. The marketplaces would become responsible when a review's inaccuracy creates problems for a buyer.
US, Hong Kong and International copyright law, as well as Amazon and AliExpress terms, do not assign review copyrights to the marketplaces.
As per Amazon's Conditions of Use page:
If you do post content or submit material, and unless we indicate otherwise, you grant Amazon a nonexclusive, royalty-free, perpetual, irrevocable, and fully sublicensable right to use, reproduce, modify, adapt, publish, perform, translate, create derivative works from, distribute, and display such content throughout the world in any media. You grant Amazon and sublicensees the right to use the name that you submit in connection with such content, if they choose.
AliExpress's Terms of Use are similar but use more complex language.
Please do not take this information as legal advice. If you have any concerns or want more details on a different country's laws, please consult with an attorney.