JUST BUCK ALREADY!

They’re blushing because they were thinking of rubbing noses in public. They didn’t, but they thought about it.

@TheAntiCat  
About what? About shippers being stupid and annoying? Guess you’re right..

Ear blush!

@Background Pony #19FC  
And there is precisely nothing you can do about it.
 
Aside from just get over it and move on with your life.

Dat lip bite by Marble!

@Background Pony #19FC  
And I agree with you that shipping is dumb but the effects on the fandom are really fun! Much better than the shipping itself.

@Background Pony #1D0F  
And you are the good example of why some people despise shipping and shippers alike, way to go keep proving my point.

@Background Pony #19FC
 
If they ever want to ship any of them, they should do it at the season finale, just like they did with Korra.  
“Oh yeah, your beloved waifu is now in a relationship that it isn’t with your OTP/your OC/you! And the series is over so you can do anything. Deal with it.”
 
Oh, that would be glorious.

@Poptard  
>The show originally had a rule of no romances for the mane cast, and considering the paltry effort and vitriolic reaction when that tradition was subverted, seems things weren’t going anywhere for any of the cast.
 
And it’s good, I hope it stays that way. Ships like this one, I can get behind of, but main cast should remain untouched.

@Scrounge  
Sometimes, I just have to give piss the upper hand.
 
Next time I’ll be ready!

@Keith Mowz  
They’re possibly still related enough for it to be somewhat taboo, though. Perhaps just scandalous enough to make things more interesting?
 
 
@TheAntiCat  
Yes you should have.

@Scrounge  
I should have expected that pun.  

@Background Pony #1F81  
Their 4+ generations previous link was through marriage, not through common ancestry.
 
They aren’t biologically related any more than any two given earth ponies are.

@Background Pony #1D16  
I think this comment really helps to illustrate it a lot better: https://derpiboo.ru/1009358#comment_562c3a79e595f03eb70001b7

@Background Pony #1F81  
Thank you. It’s that it was just a burning question.

@Background Pony #1D16  
Not really, even if Pinkie and AJ are slightly related, Marble Pie and Big Macintosh are so far removed from each other genetically that it doesn’t even matter.

This might come off as dumb but wouldn’t this count as slightly incestuous. Y’know with the whole “Pinkie and Apple family possibly related” thing.

@SeraphimDawn  
In all fairness. the Twilight in Friendship Games wasn’t the same Twilight, so it’s probably for the best that she didn’t spend much time around Flash, otherwise we’d have had to put up with a bunch of “He’s cheating on Twilight with Twilight!” and “Is it cheating on someone if the other girl is also them?”

@Scrounge  

@SeraphimDawn  
They even got a two-pack of toys declaring them a couple and absolutely nothing in the movie. Dammit, if only I could have seen it coming, like with the literal hundreds of other toys and other assorted merchandise whose descriptions were proven inconsistent with canon.

I hope these two have a long and happy relationship. After all, if they broke up, Big Mac would lose his Marbles.
 
@CogWeaver  
There was also Rarity and Trenderhoof, but nobody really takes that seriously either as far as I know.

@SeraphimDawn  
On Friendship Games’ part.

@Poptard  
And I thought they said we’d see more on the “blossoming romantic relationship” between Flash and Twilight.
 
I call  
FALSE ADVERTISEMENT!

@Mort  
It’s probably good that they didn’t tell us outright until we met Marble that Pinkie had a twin, otherwise we would all most likely be expecting another insanely-hyper pony like Pinkie rather than the calm, sweet, and shy character Marble is.
 
@Poptard  
Which of the mane six have had attempts to have relationships, exactly?  
There’s Twilight and Flash. (Which we all know how the fandom reacted to that)  
There was Rarity and Blueblood in s1 (though Rarity was always kind of the exception to the tradition you mentioned, being a more romantic type in her very character).  
There was Applejack and Trenderhoof. (Which for the most part isn’t really taken seriously by anyone in the fandom)  
I can’t think of any others, other than the sort of assumed or implied ships like Pinkie and Cheese Sandwich, but none of those have had any outright relationship-status like the previous three listed.  
I mean, I guess there’s the ever-present Spike and Rarity pairing, but even the general attitude in the show treats the idea like just a cute childhood crush and nothing serious.
 
So I guess there’s not really much in the ways of serious relationship with the mane 6. It probably has something to do with how intimately we know these main characters, and throwing a side-character we know little about at them just seems to feel kind of wrong. Which is probably why Sparity is considered something serious by many in the fandom, because we know Spike just about as well as the 6 (despite the fact that many others argue he’s just a little kid compared to them, and thus it wouldn’t ever be anything serious).  
I’d say if there was ever to be a break in the tradition you mentioned, it’d need to be done with characters we’ve come to know about as well as our main cast members. Which could be difficult, given the nature of always following the mane 6 in one way or another, but it’s not impossible.