Because it seems logic and Narida class builder confirmed it, I was thinking the melee enhancing weapon mod did not effect shadow strike (which is a sword attack and a melee) ...
It s not the case from what I have read tonight, is it ?
All other passive power amp are working on SS too ?
Anything that increases the damage you do by a % (Melee upgrades on the Fitness tree, melee mods on your weapon, melee enhancers on the weapon bonus, etc) will increase the damage of SS, as well as power bonuses.
Omni blade, strength enhancer and power amplifiers (both consumable and the weapon mod on pistols and smgs) all contribute to SS. Also the melee bonus from fitness evo 5a.