Just one of the many life skills that can be learned form New Yorkers. 
I look for the shortest line too, but women count as two people for that purpose.
As noted on the Simpsons:
No. I will question someone that is intentionally rude or commits some actually egregious offense but I’m not getting worked up over people just being people.
Hey, he’s got to learn how to snark. He’ll be a teenager some day & grateful for his training…
(I wouldn’t snark at the situation. Especially at this time of year–tempers are high enough at Target. Besides, this is Texas; they might be armed!)
Serious question: How old are you?
this woman doesn’t. i say hello, swipe my card, and leave. transaction takes about 30 seconds since i usually have an express lane amount of items.
A few months ago, a guy tried to cut me in an express line. While I think I was technically over the limit (something like I had 17 in a 15 line or similarly close), cutting is not the answer. When I said “Excuse me, but I was behind that guy,” he stared into my cart, mentally counted my stuff, and glared at me as he got back behind me.
I normally don’t go over the limit, or if I do only by a couple (by number of total items, not numbers of kinds of things), but I figure I am generally super fast, so I don’t really worry too much about it, and I am a big person for following the rules.
I will use a carriage, even if it is an express lane. I’m not going to carry a 12-pack of soda around the store and 8 jars of baby food just so someone doesn’t get offended I might be using the “wrong” lane when I’d be very clearly under.
When I cashiered express lanes, if someone came uninvited way, way over the limit, after I was done ringing them up, I’d say “Just so you know for next time, this is an express lane.” I wouldn’t refuse them service, but I didn’t want to see them back there the next day, as express lanes often just have a counter and not a moving belt, which makes big orders really hard to process. Also, the other customers in line would hear me say something to the “bad” customer and not be assholes to me about it when it was their turn.
Kinda off topic, but what surprises me is the number of people that would stay quiet for fear of being beaten up.
Is shopping in America really that dangerous and violent that you’re going get a smackdown for telling someone they have broken the rules?
No. The board just skews this way for some reason. I’ve spoken up in public any number of times and rarely had anything more aggressive than a “mind your own damn business” tossed back at me.
Not really, but I get snarky in general 
I usually assume that they may have been specifically waved over by a cashier due to other lines being busy when the express lane isn’t. Not specifically express lanes but tonight the pharmacy was so busy areas that generally don’t do general checkouts (the actual pharmacy check out, photo area) were repeatedly paging overhead encouraging customers to come check out in those area.
If I have been waved over and after I get in line but before start actually being checked out and a person with the 10 items gets behind me, I offer to let them jump ahead of me.
No, but, in general, I don’t get snarky with people offline, unless it’s someone I know well–and even then only after I know they’ll receive it as intended. One person’s snark is another person’s fighting words.