@Wesley Foxx  
I wouldn’t say that, after all in the game when Asriel dies his soul disappears as expected and his essence is spread on the flowers, meaning flower gained his memories, but treats not the same as a consciousness or a soul, especially since in undertale it’s said that not only does the soul exist but it is the center of an entity’s consciousness(if they have a soul). So according to undertales metaphysics he really is just a sentient imperfect copy of Asriel and not the real thing, he’s basically an echo.  
Also that wouldn’t be the same kind of argument as saying that when you sleep you die because when you sleep your consciousness doesn’t end it just diminishes but continues, otherwise you couldn’t dream, not to mention your brain. When you die well… it all ends, at least in the physical worldsas far as science can tell as we have no way of telling if there is some kind of soul that continues.

@TheAbridgenator  
That’s some pretty philosophical shit, though, like the same line of arguing that says that every time you go to sleep you die.

@TheAbridgenator  
Pff, you’re just hand waving your own headcanon around now. :P

@Firefanatic  
Yeah, but that’s kind of the elephant in the room with Asriel/Flowey, the thing fans don’t really want to admit: Flowey was never actually Asriel. He is, at best, a construct with his memories, who can regain his morality thanks to the artificial soul he receives in Pacifist. He’s basically an advanced copy of Asriel and that’s it; Asriel is long, LONG dead, and it’s impossible to bring him back.

@TheAbridgenator  
And that depends on whether she can feel souls or not, I suppose.

@BarryFromMars  
Well, that depends on whether Celestia considers Flowey to actually be Asriel.

@TheAbridgenator
 
The story’s not over, is it, until the reconciliation?

@TheAbridgenator  
Truly a fortunate day for those underground.

A simple reason why they can’t just fly back up is that the barrier extends through the rock and everything all the way around the underground. There’s an ‘opening’ on the top of Mt Ebott in the sense that there’s a physical hole in the earth, but the barrier covers that at some point, so that things can only go through one way like everywhere else in the barrier.

@Finagle070
 
I don’t know, nearly dying in her fierce battle with Nightmare Moon? Kinda makes one question their godhood and immortality. Then while she was recovering she… fell down the hole?
 
Honestly, I didn’t put much thought into it; I just needed some reason for her not to be able to fly back up.
 
It’s cool though; healthy doses of butterscotch pie will perk her right up, surely.

And then Celestia uses her immense magical power and Determination to evaporate the barrier, help reconcile the issues between the main characters, and join Sans in crushing the wicked Chara and trapping him inside a bootlegged version of Majora’s Mask in some old man’s garage.
 

WTF happened to Celestia?! What could have hurt an immortal sun goddess THAT badly?!