How does Shen's taunt DMG reduction work?

When you taunt people with his E his tooltip says damage taken from basic attack by taunted enemies are reduced by 50%.

So my question is does this work with on hit effects too.

For example, riven's passive hits, nasus' Q, xin Zhao's Q, and others have their damage reduced by 50% if shen taunts them?

Also does this damage reduction have effect on true damage?