I Don't Hate Cutie Marks...
As her name might suggest, Starlight Glimmer very much enjoyed the nighttime. What she did not enjoy nearly as much was early morning. which is why she might have overreacted slightly to the Cutie Mark Crusaders entering her room shortly after sunrise.
"WHAT IN CELESTIA'S NAME ARE YOU DOING IN MY ROOM?" Starlight screamed upon waking up to discover the three fillies' faces peering into hers.
The sound of the yell bounced down the crystal walls, although fortunately it didn't seem to wake anyone else up. Starlight calmed down just enough to ask in a quieter voice. "Er, why are you three in my room?"
"We just wanted to know if you had heard about any cutie mark problems," Sweetie Belle responded, a little shocked from Starlight's outburst.
"We didn't mean to disturb ya or nothin'," Apple Bloom added.
"So... have you heard anything?" Scootaloo asked eagerly. She misinterpreted the look of extreme tiredness on Starlight's face and quickly added, "Sorry. Forgot you hated cutie marks. I guess we'll go ask Spike..."
The three fillies shot off before Starlight even had a chance to gather her thoughts for a response. "I-" she started, and then shook her head.
"What was that all about?" Twilight asked, poking her head into Starlight's room.
"I, well- um, I don't really know."
"Want to come into the library? I've got a project I could use some help on. Spike's making pancakes, by the way; he'll bring them to the library if I ask him."
"Sure."
...
"Twilight?" Starlight asked as she scanned through the library for books related to griffon history.
"Yes, Starlight?"
"Do you think that I hate cutie marks?"
"Do I- hmm. Well, I know you forced a whole village to have the same cutie mark, for 'equality,' and this all started because your best friend got his cutie mark. Based on that, I would answer yes. Why?"
"I don't. And now those three fillies seem to think I do, and I'm just wondering how many ponies think I do, because I don't."
"Hmm."
Spike brought in the pancakes, placed them on a table in the library, and walked out. Hastily, Twilight swept all the books off the table and placed them in neat piles on the floor with her magic.
"So, if you don't hate cutie marks, why were you so devastated when Sunburst got his?" Twilight asked as she poured syrup over her pancakes.
Starlight hesitated. "Well, we were best friends. You know that. And just to start you can imagine it's devastating to have your best friend move away without telling you, and never have them speak or write."
Twilight nodded, the image of a cream-colored mare with a red and purple mane and tail styled much like her own flashing into her head. "Sometimes you just don't realize the consequences. Small things, like one- well, like one party missed - they add up."
"Yeah. So I was upset about that, and of course I blamed his disappearance on the cutie mark. But there was more to it than that. We did everything together - and when I say that, most of the time, I mean we practiced magic together. So he got shipped off to an elite magical school in Canterlot, where I thought he would go on to do great things, like, oh, becoming an important wizard."
"Crystaller," Twilight corrected gently.
"Well. He got shipped off to Canterlot, and I was stuck in my town in the middle of nowhere. We had always hoped we'd get our cutie marks together, go to magic school together, become wizards together. And him getting his cutie mark destroyed all of those dreams."
"You're magically talented too, Starlight. If you wanted, you could have gone to the same school."
"I may have the raw magical talent, but he definitely had a better idea of how to use the talent he had, and that's what got him in. He could have simply saved me from the stack of books the day he got his cutie mark, but he shelved all the books as well. It's that precision that set him above me. Besides, even with my raw talent, my parents couldn't afford to send me to Canterlot."
"Oh, Starlight, I'm so sorry." Twilight reached out to wrap a wing around her friend, but Starlight gently shoved it away. "I'm not finished ranting, Twilight."
"Of course." Twilight stacked their plates at one end of the table and levitated all the books back up. "Please continue."
"So I was jealous. And the cutie mark and the event that caused it were of course easy to blame. I wanted to be the best! I had the talent! Why wasn't I the one being sent off to magic school? It didn't seem fair. I dreamed of a place where I could be the leader, a place where I'd be better than anyone else: Utopia."
"Your town - wait, it had a name?"
"Yeah..."
"Okay. Utopia."
"Yes. Anyway, the third reason I created Utopia is simple: I was jealous that the first thing he did when he got his cutie mark was to run off and show everypony except me: the pony who helped him get it in the first place. This was betrayal of our friendship. I wanted friendships where nopony would abandon me. If I needed to force such a friendship- well, I was absolutely fine with that."
Twilight opened her mouth, but couldn't think of a comment. Finally, she closed her mouth and shook her head.
"And finally, everypony looked down on me as a blank flank. That's the real reason for Utopia. I resented the use of cutie marks as a status symbol, rather than a symbol of talent or destiny. I truly did dream of a world where everypony was equal, and didn't look down on others, but I went beyond equal, into sameness. It's... awful, really. I'm really sorry I removed your cutie mark, Twilight. And I'm really sorry for everything I've done. Oh Luna, I hate myself so much right now..."
"It's okay, Starlight. I've done some pretty awful things too - ever tried forcing a whole town to chase after a doll? And that's just one example. For now, though, could we get back to griffon history?"
Starlight smiled, bowing her head gratefully for Twilight's forgiveness. Then she levitated a book and began scanning through it.
"And Starlight?"
"Yeah?"
"I'm guessing Sunburst didn't mean to ignore you while he was at Canterlot. There just happened to be a lot of drama with his sister at the time."
"His sister?"
"Yeah. My friend Sunset Shimmer."
Twilight hastily rescued the book with her magic as Starlight dropped it in shock.
Author's Note
Wow, that took a surprisingly long time to write. Curse you slow fingers, who, despite two years of typing classes, still cannot type! Anyways, hopefully this chapter is over 1000 words, otherwise I won't be able to post it and that would make me sad.
griffin/griffon/gryphon
You know... the thing with a lion butt and eagle face. That thing.
Do ponies use syrup for their pancakes? I genuinely don't know.
And yes, I named Starlight's town "Utopia." I thought it was a fitting name.
Sunburst/Sunset Shimmer as brother/sister? Anyone?
Probably not going to be great, to be completely honest. 
Oh well. 