Apps
If the setting “Share with app developers” in the macOS System Settings under Privacy & Security > Analytics & Improvements is enabled, crash reports which are not linked to the user are shared through Apple and used for the only purpose of fixing issues within the apps.
Website
When leaving a comment, the IP address is saved along with the user-provided data. The name and comment can be made public unless requested otherwise; the other data, including the email address, is not shared.
The Google reCAPTCHA service is used to protect against spam comments.