ATMega32u4 output power to input without external resistor?
Yes, you can drive a High Impedance (Hi-Z) input directly from a General Purpose Output (or GPIO) pin without a resistor. Neither a pull-up or series resistor is required.

The only concern is that you must never ever switch that input pin to output high or output low. If you do,  you'd create a dead short, burning one or both pins, their pin ports, the microcontroller, the regulator, power supply, etc. 

A series resistor is useful to prevent this from happening, by keeping any accidental short to a few mA, not Amps. At a few cents, it's cheaper than your clone board. 10k to 47k ohms or so is fine.