Disconnect the fan cable from the socket so that the motor doesn't send pulses of energy back into your laptop. It probably won't harm it, but better safe than sorry.
So you "disprove" my statement with some rando on the Arduino message board that has less than 20 posts in their lifetime?
What makes you think they're an authority?
Brushless motor still have fly back voltage that has to be clamped. You may not need to install a diode in the fan, but I can guarantee you that this "inbuilt driver circuit" has such a diode.
And if you read the linked thread a bit more you'd see where they test it and it does produce -100V at shutdown. If there wasn't a flyback diodes it'd be burning out ic's left and right
Disconnect the fan cable from the socket so that the motor doesn't send pulses of energy back into your laptop. It probably won't harm it, but better safe than sorry.