I think Zanz had it in his head that in order for something to be an ability, it has to be activated by first clicking upon the creature which has it.
He may have overlooked the numerous cards which contain passive abilities, fundamental to the very essence of what makes that card the card it is. Eg. Sundial stopping damage, as well as offering an extra card pick-up.
Perhaps your confusion is that Zanzarino never said it? A link would be nice
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The way I see it is; cards can have as many passive abilities as you can give it, but only one active ability at a time. Ie. Adrenaline, Antimatter and Momentum all stack on a creature, allowing it to keep its original ability... Devour, Lobotomize, Spawn Firefly or Mutate for example.