Does the piercing mod allow me to shoot through cover/objects?

The description for the Piercing Mod says:

Allows bullets to pierce 0.50-meter thick objects, but at 60% reduced damage. Ignores 25.00% of defenses on armored targets.

0.5m, or 50cm, seems quite a lot. A lot of the columns/crates/benches etc. that provide cover in the game are easily less than this. Can I shoot through them?

The Piercing Mod description is giving you a maximum distance you can shoot through, not a minimum. It means it won't shoot through things thicker than .5 meters, so yes, anything thinner than half a meter will be penetrated with no problem.

I'm pretty sure they picked .5 meters because that's roughly the size of most of the cover walls in the game.