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Unless the protocol itself is changed where it's possible to move coin without private key.
How can non-mining nodes change the Protocol?
UASF, UAHF, use client which follow different protocol, etc.
Non-mining full-nodes cannot change the protocol.
This can only be done by miners.
WRONG! BIP-148, also known as the User Activated Soft Fork, actually showed that the miners do not vote. The community running full nodes do. The miners simply followed, and gave the full nodes the type of blocks that full nodes demanded.