It's literally like reading a guide "How to kill yourself with an MRI machine" and following it step by step

Dude, exactly what I was thinking. Even if the staff weren’t telling me to remove it I would instinctively do the math:

big fat metal chain + big fat powerful magnet = disaster.

In fact, whenever I hear MRI I instantly think dental fillings. You’d think the patients and their handlers would instinctively think about all the metal they carry. How could big fat metal chain on neck not come to mind?

Step 1: Affix excessively large metallic decapitation device.

Step 2: Lock metallic decapitation device in place.