No she does'nt. The skeleton key opens the door, nothing to do with Nocturnal.
The skeleton key opens doors you can't usually see, it's no diferent to the others it opens.
What are you talking about? You didn't use the Skeleton key to get out of Irkngthand, the rocks collapsed by themselves. These are things under the influence of Nocturnal. Luck. She saved your life.
I guess if you are talking about serious Rping standards I guess you're right.... Since skyrim is base on heavy religious practice. However Nocturnal did not mysteriously appear out of no where while the the room was being flooded with water. If you remember hard enough their was a lot of rumbling that was occurring at the time after you kill Mercer. I can't for one moment connect Nocturnal with the rocks on top of the building from falling . If you look closer (when you do the quest the next time) the rocks was already severely unstable, and with the rumbling going on it was going to happen no matter what. Oh and Mercer Frey was an intelligent man with good tactician under his belt. What if he was the one that made the rocks so unstable? Maybe that was his escape route had he won the fight against the dragonborn, Karliah and Brynjolf.
Again Nocturnal had no part of this whatsoever.
I'm not saying that the rocks weren't already loose. I'm saying it was the luck of Nocturnal that made the rocks shift in that particular way and open up this entrance to a secret tunnel. I'm not arguing how exactly it happened, I'm saying that just as all seemed lost,
luck got you out. Gallus says this when you meet him in the Twilight Sepulcher. That you should never doubt your skill as a thief, but Nocturnal gives you little pieces of luck.
Also, you think Mercer actually planned the rocks to fall that way? The man must be smart and he does have the Skeleton Key, but that's looking a bit into it. I think he would have found a way to get out through the doors he had blocked off that you entered through.
Again, I see no reason why you guys don't believe that Nocturnal helped you.