Social etiquette/quirks in your region/country

[Chessrook44]

Pah. Soda, Pop, Fizzy, Fizzy soda pop...

I drink Coke. Even if it's Pepsi, it's still Coke.

 

[Dimitriov]

German speaking and most Slavic countries:

If you meet someone for the first time, address them in plural.
If you talk to someone you are not on very friendly terms with, address them in plural.
If you wish to express respect towards someone, address them in plural.
If you talk to someone older than you, address them in plural.

Children used to have to address their parents in plural.

Some foreign companies even got in hot water for not addressing their customers in plural on their billboards (IKEA).

Weird concept to explain to someone in english.

Do you mean the plural second-person pronoun? Because that would make a kind of sense. Indeed, if I remember aright, English used to be the same a long time ago.

Thou/Thee was the singular and more familiar form, while Ye/You was the plural and more formal. Somehow we've lost all that and ended up with only the objective plural. Not that too many English speakers today would know that...

On -Topic Edit:

I love this, because it rings so true: