Hi! New player here with a question.

First, the relevant game effects:

Lightsaber Deflection

Interrupt: When damage is dealt to a friendly non-Vehicle unit, deal 1 point of that damage to another target unit instead.

Always resolve interrupts to a triggering condition before resolving the effects of the triggering condition itself.

In a recent scenario, during an engagement, my unit with 1 damage capacity was dealt 2 unit damage from an opposing unit.

Can I play Lightsaber Deflection to redirect 1 of the 2 damage, even though my unit will still be destroyed anyway?

Someone told me that the act of "when a unit is destroyed" is itself an "interrupt," but I haven't seen rules to support that.

From what I understand with the timing rules, an interrupt actually happens before the triggering condition resolves fully.

Yep, you can use Lightsaber Deflection there. As an Interrupt, it happens before the damage is actually dealt as thus before the unit dies.