Many features have commenting capabilities that allow your users to engage with you and each other after they log into their Facebook or Twitter account. Social media login is required for user experience and accountability (users are less likely to post abusive/derogatory comments if their accounts appear next to them).
The user's profile photo and name will appear beside their comment within the app. You'll also be able to see this info in the Promote section of your app dashboard, where User Activity is located.
You can monitor comments under the Comments section that appears under relevant features within the Build step.
To delete a comment, simply check the box to its left, then click the trash can icon.