Quote from Anachronity »If you're asking whether Portal Mage would redirect Kozilek's annihilator trigger to the new defending player, then yes. It would.
If you used Portal Mage against Colossal Whale, its ability would fizzle because it specifies "target creature defending player controls", but the creature targeted no longer belongs to the defending player (because Portal Mage changed who the defending player is). This is like how if I were to Go For The Throat your creature, the spell would fizzle if you made that creature an artifact creature in response. This is what that last ruling you cited is trying to say.
Conversely, Kozilek's ability doesn't target. It causes the defending player to sacrifice four permanents. The defending player has changed by the time the ability resolves, but that doesn't matter; there are no targets that have been selected and so the ability still resolves and still affects the (new) defending player.
This would have been my understanding but others in the thread seem to disagree? I'm still a bit confused myself.