To switch 'Product Reviews' on/off on product pages, from the store dashboard go to:
> Store Settings > Products > Reviews

From within this page, the top tick-box labelled 'Show Reviews' will either enable or disable the feature.
*All reviews are imported from previous buyers of your products on AliExpress*
You are also able to 'Show date for each review' and 'Show country flag for each review'.
'Allow users to add reviews' is also another feature that enables/disables the opportunity for your customers to leave reviews.
Lastly, you have the option to ask your customers to agree to 'Terms & Conditions' before they leave comment. This can be enabled/disabled by checking/unchecking the tick box labelled, 'Show T&Cs and require user to tick to agree'.
(*Don't forget to click 'Save Changes' after making alterations*)