Originally Posted by
baliktad
The companion cert isn't really anything special. It's basically a way to override the price of a 2nd ticket when purchasing two at a time. Other than that price override, EVERYTHING else about a companion ticket is EXACTLY the same as any other 2-ticket purchase.
Since you can use your e-wallet credit when buying a 2-ticket purchase, you can use your e-wallet credit when buying a companion fare.
But you can't use a e-wallet discount code ie worth $100 in conjunction with a companion fare. Alaska airlines confirmed this at least to me.