In the HTML export -> Comments and sharing section of Project settings dialog you can configure comments (e.g. to collect feedback) and social networks sharing buttons that can be added to your exported HTML files.
To open the project settings, use one of the ways described below:
Use this field to specify the number of Facebook comments to show initially when page is loaded. Users can load more comments by clicking the corresponding button or icon at the bottom of the comments section.
If you want to moderate comments and receive notification about new comments in your Facebook account then you must provide either your Facebook User ID or Facebook Application ID.
Use this field to specify URL of a custom image to display on social networks when someone shares a link to a page of your documentation. If the URL is empty then an image will be chosen automatically. Usually it's the main image on the shared page.