You can configure your SiteGround Ecommerce site to allow reviews from Everyone, Verified Customers, or you can disable the reviews entirely.
How to Manage Review Settings:
- Click on Settings
 

- Click the Who Can Post Product Reviews dropdown menu
 

- If you select Everyone, any visitor would be able to post a review on a product.
 - Select No one if you wish to disable product reviews entirely.
 
Each existing review can be approved, unapproved, or deleted entirely: