Social Snowball allows you to choose whether you want to track a referral sale coming via an affiliate's Safelink using cookies or not.
To set up Safelinks, please refer to this tutorial.
You can enable/disable this in the Advanced section of the Settings tab in your dashboard.
Scroll all the way down to Safelinks Cookie Tracking section and toggle it on/off.
By default, this option is enabled. However, if you disable it, Safelinks will only track via discount codes and not cookies.