@ShimmeringStallion  
The only major difference is the narcissism aspect in this comic from Luna, which ignores and character development with making friends with masses. The idea of falling in love with a mirror image of yourself on the basis of ‘they know me best’ has been done in fiction for ages.

@ShimmeringStallion  
Sure :)
 
Since these nigh identical lines of dialogue are prevalent throughout the webcomic, listing all the ones that parallel the dialogue from Moony in the last 10 pages would be an incredibly difficult task.
 
That being said, even gathering a small example of pages is no problem.
 
This and This and This and This and this are just a fifth of the dialogue in El Goonish Shive between the magical clone Ellen, who’s ‘Moony’ in this case, and her original, Elliot (Luna in this case), and the other party responsible, Tedd(Celestia in this case)…that lines up almost identically with this storyline. Besides the obvious personality and situation differences, they are tat for tat.
 
Its an interesting type of story, don’t get me wrong, but it situationally makes no sense in MLP Luna’s setting. For Moony to be fully sentient, like Piccolo from DBZ, while Luna is still herself, that would mean that Luna is completely without her negative emotions, her shadow self. If they were two halves separated, that would make more sense, but this comic’s logic is that her darkness is now completely separate from Luna, making Luna incapable of falling back into dark corruption on her own since she literally doesn’t have it. I just don’t see how that makes sense.

@CronoM  
You really SHOULD back your words up…

Isn’t this guy just ripping off dialogue from the webcomic El Goonish Shive?
 
I’m not even kidding. Some of these sentences are almost word for word. Jeezus…

@Background Pony #0B2A  
Considering “Lesson Zero,” it’s a terrifying thought, what could spawn from sparklebutt’s mind…

@Tetrominon  
Well, so long as it’s not an Equestrian insult, I’m fairly sure it’s fine to say.
 
… Like calling aliens Goobacks

@ShimmeringStallion  
Isn’t that a Tamrielic insult?

You shall call her “Mare without a Shadow”… or “MWAS”.

Eh, just check its complicated on your relationship status on Ponyhoof.

“Moonbutt.” Call her Moonbutt.

Nightmare: Are you my sister, my mother, or myself?
 
Mugen: Better question. Who cares?

I think Nightmare Moon is a creation of Luna,like the Tantibus.I think any alicorn can create an entity with only a thought…  
I would keep an eye on Twilight,Cadence and Celestia,some big emotional stress can break them.

@Background Pony #8D92  
It was a joke.

Narcissism brought to a new level.

(Silently adds existential crisis tag)

@PonyPon  
That’s actually a good sign.

@Background Pony #BB67
 
Pretty sure that ponies are fictional, and therefore can’t be offended by something written on an image sharing site.

Forget it, Luna. It’s Chinatown.

@Background Pony #BB67  
The comment you replied to is the farthest thing from a reason to write personal attack. <.<

@Dannyson97  
You know who’s narcissistic? You are. Don’t offend others (even if they’re ponies), as you are so amazing, okay? Let them just enjoy the advantages of their lives.

Luna x NMM? I’d ship it

So … Nightmare Moon was Luna’s tulpa ?  
New headcanon accepted.

then Luna says “you just need to call me my love/dear/wife etc etc…”

Inb4 “It’s not incest, it’s masturbation!” joke

In hindsight seems rather narcissistic of Luna to fall in love with herself like this. That’s probably why no one talked to you 1000 years ago Luna.