
Google AdWords will stop displaying review extensions in mid-January 2018.
All review extensions and their performance data will be deleted from AdWords accounts in early February.
AdWords ad extension data can be downloaded by going to the Ads & extensions page and clicking on Extensions.
This change was stated in advertising policies help document. And this change could possibly be a blow to third-party review sites, as the reviews displayed in the extensions came from non-Google websites.