I've been told that Life Model Decoy nullifies the unavoidable damage that Red Skull can possibly take from the Cosmic Cube.

Is there any validity in this?

No.
It deals unavoidable damage. What's that?
Feat cards are not a power, but they are an effect - therefore it would not work.

It will work on the PENETRATING damage of Parasite's and Adaptoid's Drain powers, though. (Any penetrating damage can be reduced by this actually.)

penetrating damage: Damage that can’t be reduced by powers that reduce damage dealt.

LMD is not a POWER.

"What's That?" can I get a "WHAT WHAT?" LOL , nbperp style of teaching is simply brilliant. I almost visualized a claymation of Hulk Hogan doing his classic wave of the ear motion.