I've been blindly adding piecing damage mods to swords, and giving up a few dmg points in armour for a relic with a high piecing damage bonus.

But looking at the stats sheet, I've noticed that the only place piecing damage is listed is under cross bows. I don't know how to dig into the bowels of the game to find out whether the piecing damage stat, affects swords or not.

Can anyone factually provide proof one way or the other, or point me to a reliable reference?

Thanking you in advance.

I posted on this a few days ago. Apparently no one really understands how it works, we all just blindly assume it does what we want it to do.