For more details see the Facebook Comments for Magento 2 extension page.
The extension allows you to improve your business Facebook presence and significantly live up your product pages. Let customers share their views with their friends and potential clients. Get more reliability and trust for your company name.
To configure the extension, please go to Admin panel → Stores → Configuration → Facebook comments.
Review Title - Choose a name for comments and reviews block.
Reviews per Page - Set the appropriate amount of comments per single product page.
Chronological Order - Select Yes, to display comments in a chronological order.
No - to display the newest first.
Block width (px) - Set an appropriate width of the comments' block in pixels.
No default styles - Choose whether to use default CSS styles or set a Custom CSS.
When you finish with the configuration, you have one more block (e.g. Facebook Reviews) next to the blocks with Details, More Information, and site Reviews.
To post a review, a customer has to log in with Facebook account.
Also post on Facebook - Customers can share their opinions with friends and duplicate their reviews to the their Facebook feed.
There are various options to work with comments. Simply click on the arrow on the comment field to have a drop-down with options. For customers, it is possible to Collapse, Edit, Delete or Embed a comment. For merchants, to Embed, Collapse and Report a customer's comment, if it is inappropriate or irrelevant.
When you want to Embed a comment, you can use a preview and advanced settings to customize it, then share.
Sort by Newest - It is also possible to sort comments, while on the front-end. Display Newest reviews or display reviews chronologically, depending on your demands.