>>Participation in an abortion results in automatic excommunication.<<
It’s the age-old question: If a tree falls in the forest, and there is no one to hear it, does it make any noise.” So too with automatic excommunication. If no one hears about it, does anyone know?
The purpose of public excommunication is to expose the sinner in hopes that the sinner has a change of heart.
The purpose of excommunication is to remove someone from union with the Church; the public matter would apply to a public act.