F. Bertolazzi:
No, I did not write it. ;-)
Atmel's AVR MCUs are fairly well ESD protected (never had such a failure), put their clamp diodes cannot take more than 0,5 mA.
No, it cannot. But it's not a problem: with an 8 bit expander you can use two lines for clock and LD/SH and four lines for reading in parallel the data from the four HC165s (including shorted drivers and open load detectors).