#the idea that people need to drink at parties is something i adamantly disagree with

[iturbide]

On the matter of Chrom and Robin and their drunken states, I absolutely think context matters. If Chrom's getting drunk because it's a party, then he absolutely becomes the person with a Single Braincell and stupid shit is bound to happen. Robin's still a lightweight but a drink or two wouldn't be a problem for a celebration. On the other hand, when they're alone? Then yes, the underlying fears come out, hard.

This is extremely true but at the same time, I still think it plays into the amount they’re drinking.  If it’s a party, Chrom’s not going to go all-out: he’s going to drink a comfortable amount with probably a decent space between each one, and he’s going to be eating along with it.  Both the timing and the meal help to mitigate the effects of the alcohol, so he’s not going to get into a really deeply inebriated state that leaves him morose in a party/celebratory context.  

Robin doesn’t like to drink in the first place, and wouldn’t feel a need to drink in a party situation: the rest of the Shepherds have figured this out and completely respect that decision, so they don’t pressure Robin to drink, instead providing something like spiced cider.  Anything they drink at a party would have minimal to absent alcohol content, and no one would mind – in fact, if someone did try to either spike Robin’s drink or pressure them into drinking when they don’t like it, the Shepherds would kick them out.

The only time Chrom or Robin would get really drunk is when they’re in a bad state – like the aforementioned conflict between Validar and the Exalt that they’re having to moderate.  Chrom tends to get drunk when he’s depressed.  Robin, again, doesn’t drink, so when they do, it’s kind of a big deal and means that something is wrong.  Chrom knows this extremely well, so if he were to find Robin trying to get drunk, that would be a huge red flag and he would drop everything to try and figure out what’s going on.