Good is boring. That’s all there really is to it.
 
Also, she technically achieved Hitler’s dream of a thousand year empire.

As weird as it is, I like to think that Celestia is like how Dogma described God.
 
Wise. Lonely. But Funny.

I’ve never understood why some people seem to give this so much importance.  
It’s a parody, of course it’s going to be something related-but-not-related to the character, the more different, the better.

@PonyPon  
You know, that would be really interesting, if they went that way with Celestia. If they intentionally portrayed her as a benevolent being, who strives to benefit everyone but can’t, despite her best efforts, understand the ponies of lesser power and shorter lives, and inevitably alienates them with her well meaning actions.
 
As it is, she’s clearly supposed to be seen as an understanding, wise and otherwise perfect pony princess, which makes all the questionable stuff she does seem so glaring.

@Trickquestion  
She didn’t only sell her student, she sent Twilight and the Elements of Harmony, who banished Nightmare Moon, defeated Discord and helped defeat Chrysalis. Also, if she doesn’t send Twilight, we wouldn’t have an episode, since the show is about Twilight and her friends’ adventures. “Send the Royal Guard” doesn’t seem a very fun episode…
 
She can change a party but others, the nobles, like it… why should she deny them their fun? Then again, if Twilight and her friends attended at the party and nothing happened it probably wouldn’t be a very fun episode.

@Trickquestion  
Or doesn’t understand the effects she has on ponies.

I would also call her handling of the Crystal Empire really irresponsible. If Sombra’s as huge a threat as you want us to think he is, why are you sending your student with the worst handicap possible to take him down as a test? Sombra was seconds away from winning because Twilight has her lips super glued to your plot, and you told her to do something mind bogglingly stupid. Then again, this isn’t so much maliciousness on Celestia part, but of the awful character derailment Twi suffered in that episode.
 
And her way of dealing with the Gala is pretty stupid. You are the supreme ruler of your nation, and are worshipped/feared like a deity. If you want to change a party, just change it yourself. Who the hell is going to say no.
 
The trend seems to be Celestia consistently suffers from bad writing.

@Trickquestion  
Mediocre writing aside
 
If I were to offer an explanation that makes any sort of sense, if Celestia openly said “It’s a world filled with hairless monkey things that may or may not be dangerous” would only cause tensions to rise higher and would only make the situation more complicated than it already was.

@Itsthinking  
That seems too petty, I mean Luna’s reason for her decent into darkness was already pretty petty, but I don’t think it’s as simple as a sibling rivalry.

@nopony_you_know  
Celestia says she had no idea what’s on the other side of the mirror, meaning she never even mounted a cursory exploration. So, the reason you’re suggesting is something Celestia didn’t know, because she never even bothered to glance through the mirror, even after her student went through.
 
Though, as I said, I attribute that to EG’s terrible writing then any moral defect on Celestia’s part.

I detest molestia and tyrantlestia.
 
Trollestia however is just funny.

@nopony_you_know
 
@Trickquestion  
Dammit didn’t mean to do that. Anyway, it’s not like she could just get her without making a scene especially with her human self only arms distance away.

Oh, and I’m not a Lunafan either. I think both of the sisters probably acted badly towards each other and can only assume that they let their sibling issues get in the way of ruling.
 
I suppose we’ll see more about this in the S4 premiere.

@Der_Fur_Shur  
Just leaving Sunset in the human world without even trying to get her back was a bit cold though.
 
Then again, I’m not about to begrudge a character over something they did in Equestria Girls.

@Der_Fur_Shur
 
I know that feel.

Oh great now it posts my comment just when I make a second one so now there’s two I suppose

@Itsthinking  
-Prevented her sister from enslaving and possibly starving the entire kingdom, if not the entire world
 
-Raised said assistant until he was old enough to take on said responsibilities
 
-Indirectly led her student to finding the greatest friends she’d ever have and prevented her from living what would have probably been a far less fulfilling life

@Itsthinking  
-Stopped her sister from taking over, enslaving, and (assuming photosynthesis works the same way in their world) starving out the entire kingdom and possible world
 
-Raised said assistance until he was old enough to take on said responsibilities
 
-Laid the groundwork for her student finding the greatest friends she’ll ever have and indirectly saved her from a lifetime of loneliness
 
Celestia is a leader yes, and she does hail from the Dumbledore school of mentoring, and yet nothing justifies the crap she gets

Suddenly. Luna fans.

Let me count the ways:
 

???

You mean only a small part of the fandom?  
Not everyone is like that. I’m not, that’s for sure.