UnityEvent draws debug variables in the inspector

I have two MonoBehaviours with identical code, but there seems to be some serialized data outside my control that causes unwanted debug info to be drawn in the inspector.

You can see the two components below:

Any time I add a ColliderTrigger component, those debug variables are drawn. But with new copies of that script file, the problem doesn't occur.

The code looks like this: (based on instructions from the docs)

 public class ColliderTrigger : MonoBehaviour
 {
     public EventTestProperty unityActions;
 }

 [Serializable]
 public class EventTestProperty : UnityEvent<GameObject>
 {
 }

Any ideas about why this might be happening? The problem affects many of my UnityEvent scripts, but I can't send a bug report until I figure out how to reproduce the issue.

Using 4.6.2