Discount box should not be visible on non-fee events

We have several non-fee events and the CiviDiscount box is showing on all of them. I've gone through all the settings that I can think of to check, and I'm not sure where this behavior is coming from. I attempted (very quickly, admittedly) to replicate this on the demo site and was unsuccessful in not only getting a discount box to show on a non-paid event, but in getting a discount box to show an ANY event on the demo site.

You can see an example of a non-fee event with a visible discount box here:
https://www.imba.com/civicrm/event/register?id=597&reset=1