Damage Shield Penetration is inscrutible

[jenx]

I have 80% damage shield penetration on my current character, stacked, but I have no idea about:
1. if or how it works
2. if it stacks
3. what the mechanism is

so, could it be placed on the char sheet under Attack (for total, plus per weapon)
and can it be explained
AND, can it go into the log, as nothing is fluished to the log about how it works as a mechanic AFAICT