@TheRocketMan
The comics show he's an ambassador.

@Broken Adam
When Discord comes back
"Got busy there, Tia?"

@Broken Adam
Everypony in Equestria are actually distant cousins… XP

@TheRocketMan
It's been confirmed by Lauren that the "nephew" status is just a short way of saying he's slightly related to her


But it does bring the Question of "how many Nephews she has" because after 1000 years it's probably in the thousands unless if his family was insanely inbred

@lonewolf
Maybe he's just there because he's royalty, considering he's (somehow) Celestia's nephew.

@TheRocketMan
Truth be told I don't think it was supposed to be Blueballs. DHX just got lazy and reused him for another pony instead of making a completely new one.

@QueenChrysalisIsBestVillain
So he seems to be a ruler of "something" but the show never explored what that was.

@WinterCutieMark
He is in the episode "Equestria Games" sitting in the seats with the official ponies

In hindsight, it is kind of a shame for someone introduced as Celestia's nephew to never again make a appearance. Was he banished to the other end of Equestria or something? You would think that he would be around more often with that kind of connection to Princess Celestia herself. I mean, is he even seen in the background past season 1?

@Hericks
Alright, man. Whatever.

@TheSultanAkbar
Along with snide remarks. Jerk.
I guess they don't teach proper mannerism where you are, Mr. "You must be from USA".

For the record, making snide remarks and telling people "stfu" is NOT good mannerism nor does it promote good holiday spirit.
I am NOT misunderstanding you, you're just being a douche. Knock it off.

@Frustration in Excelsis
Jesus. I don't think he understood me. I was saying how it was new years!

@TheSultanAkbar
@Hericks

I think it's probably best if you all drop this argument.

@TheSultanAkbar
And you are back to being a jerk.

@Frustration in Excelsis
CoughTiaraUltima&PonyPOVcough

@Hericks
Oh, ok. You must be from USA. It's new years. Just fuck it. It ain't worth it, man. Enjoy your life. Go.

@TheSultanAkbar
Noone was even fighting. We were just having a casual discussion.

@Hericks
I think we misunderstood each othee, alright, this ain't the time for some bullshit children's show. Go spend time with your family. Have fun. Fuck this shit.

@Frustration in Excelsis
True.

@TheSultanAkbar
Why are you being an jerk? I didn't even say anything offensive, just responding to your inquiry.

@Wiimeiser
Oh yeah! Can't believe I forgot about DT.

Honestly, though, I think she fits the pattern as well, although she was a fairly important character in the context of the CMC's personal storyline. Early appearance, shallow personality, few to no likable traits, and my God did the fandom hate her -- I'm sure there was no shortage of DT torment stories, but I what jumps to mind for me is the amount of fiction where she jumps from being a spoiled kid and schoolyard bully to an out-and-out major villain.

@Frustration in Excelsis
Wow, that was the first actually well explained reason I've ever heard. Usually it's just along the lines of "He got cake on rarity! He's a marvel level villain for that so we aren't exaggerating anything!" Bravo for that.

My thing is also though a good handful of those fics gave him the most lazy non-motivations for meanness or even if he's realistically canon levels of rude they make everyone else extremely OOC.

Like one in a world where harems are legal Celestia is mad he has one. No he isn't doing anything bad to them, she's just mad he has one or sends him somewhere to be hurt or tortured for a "lesson" in being nicer. In a fic where the princesses disappear and Twilight is doing a bad job at reassuring every pony things are fine even with the Sun and moon are moving on their own suddenly.

At some point when she comes out of hiding in her room for a week to let a few select ponies know things are okay with the planets moving. He tells her she needs to not hide as princess and go calm other town ponies down since their getting paranoid.
She then goes on a rant about how he can't tell her what to do cause she remembers he was rude at that season 1 gala so he knows nothing.
Mini boast here but I've at least given a small hand at helping increase good fics with groups both on FIMfic and DA about positive portrayals of him. I don't mind if he's an antagonist in fics but if the main issue for people is that he's a one-note personality in the show then it shouldn't be that hard to give him more then one-note in your fics/fan art whether he's good or the "bad guy" in it. I genuinely hope the show does that for him in G5 or some future incarnation.

@Frustration in Excelsis
What about Diamond Tiara? You forgot about her.

@Charzoid
Personally, I believe that a lot of Blueblood's… let's say unique position originates from the earliness of his appearance. He debuted fairly in the flush of the fandom's formative period, back when every background pony and their uncle were having entire personalities extrapolated from one odd thing they were doing in one scene, the big fandom headcanons were forming, the fandom as a whole was emerging, and so on. More or less everything that happened at this time left an impression, often far in excess of its actual impact.

Blueblood is a fairly good example of this. He's a tremendously inconsequential character as-is -- he's really just a minor antagonist with minimal characterization meant to serve as a symbolic obstacle in part of one episode's plot, but he was also one of the very few antagonists, for a somewhat generous value of that term, that the fandom had back them. Of the real villains, Nightmare Moon fell into the too cool to really hate category (I mean, to this day we have some people genuinely asking "but would absolute rule under a self-centered, unhinged tyrant really be that bad?"), Trixie was… divisive on account of less-than-stellar plotting in her episode, and Gilda fell into the same general category as Nightmare Moon.

This left Blueblood as the one person the fandom had no particular reason to like. Combined with his admittedly extremely dislikable personality (that's what you get from a caricature!) and the aforementioned tendency to extrapolate entire characters out of background gags, this likely led to his early fandom perception as the spawn of Satan's loins.

From that we get the early flood of Blueblood-is-a-monster and Blueblood torment fics, which in turn leads to a sort of counterpush once people start finding this all a bit much. This all led into Blueblood's current status, where some people hate the soil he walks on, others think he has potential that was never really tapped into and needs more development, and everyone fundamentally treats him as mattering a lot more than he really does. He isn't a monster. He doesn't need more development. He's a glorified plot device who appeared in a specific role in Season 1, left the stage with little ceremony when that role was done, and was never used again.

If Blueblood had simply happened to debut later on, you'd see none of these. Later jerk characters, even ones with a lot more personality or who did worse things (Suri Polomare, Wind Rider, Svengallop, etc.) see minor use at best and are often entirely forgotten, which I would say is because they appeared too late to really cement themselves. If Blueblood had originated in a later season, he'd likewise have been largely ignored by the fandom.

You probably see things like these in most fandoms centered around long-running works, I think. I know that the Wheel of Time fandom has a similar obsession with a very minor villain who had a memorable scene in an early book, even though he was killed shortly thereafter and never played any role there again. It's more of a fandom than a hatedom, granted, but the principle is the same — overobsession with an early character who doesn't really matter all that much.