Usually, hot shoes are designed so ordinary metal accessory feet can slide in without touching the electrical contacts, which are typically recessed. In many cases, a metal cold shoe will mount safely.

However, the Sony Multi-Interface Shoe has extra contacts, and at least one pin carries battery power. If a metal foot were to bridge that pin to ground, damage or at least a blown fuse is possible. So while it may be fine in practice, there is some real risk if the accessory foot can reach the contacts.

If you want to be completely safe, insulate it: a small piece of non-conductive tape on the accessory foot or over the camera contacts will prevent any electrical short. Also check that the accessory stops before reaching the contact area and doesn’t insert far enough to touch the pins.

So: likely safe if the foot doesn’t contact the pins, but if you’re unsure, use tape or another insulating layer.