This has been interesting. I've lived here for 20 years and my parents are English and there have still been things I've just found odd. And still do. This is home now and I am very happy, but there's no doubt that there are some cultural quirks....
I've only seen one mention of the main one though.... QUEUING!? The brits queue for everything. I mean, broadly, I have no problem with queues, I think they make a lot of sense and keep things fair. But there's zero thought given to queuing more efficiently? Eg, my local pret used to have space for three queues to stop the queue going all the way back into the seating area. With signs between both queuing areas saying, "please queue both sides". But no one would. They'd all queue in the middle. I'd queue on the left or right, get served, and suffer death glares. My pret gave up and took the queue both sides sign away!
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Or queuing for the bus. I have no problem with that. But why do Brits insist on queuing single file!? It's a bus stop - there's not a lot of space. If you queue in pairs or so, you would take up a lot less space.
Totally agree with sweetcorn in every sandwich and salad. I love sweetcorn but I can't get behind it being in everything.
And yes yes to the lack of clarity. I find the meaning within other comments almost impossible to translate, even after all this time. I think I've nailed comments that are actually social cues (eg, "mmm, interesting" meaning "please stop talking" etc) but I really struggle with the fact that choosing a dinner destination or whatever can be this massively complicated minefield.