peek/poke or other method to write direct into nrf52 registers?

Does anyone ever used poke32 on a NRF52?

Oh yes, a lot - for instance with http://www.espruino.com/NRF52LL

So I think it's that particular register.

I imagine you get the 3 LEDS lighting up? That's caused by the softdevice throwing an internal error - at that point the only thing Espruino can do is to reboot.

I think realistically you might be better off trying to build your own firmware with NFC disabled - it's probably easier to do it from C-land. Or, depending on what you're trying you could unsolder the IR LED and use those pins, or perhaps use an IO expander? :)