In the original post (I assume is OP), the user asked about the usage of ‘Did you want ...?’ at some eateries. Some teachers have explained that it is an accepted version of politeness in that milieu in North America with the past tense.
Yes. "Do you want," "Did you want," "Would you like," and "Will you want" are equally polite and grammatical in the US.
People who don’t have an American accent and who are not in North America should avoid this form of usage or else be considered a grammar mistake. Unless, one shows a more convincing tone to native speakers.
Interesting to know!
I am just curious.
Thanks to the original question, I am able to learn about this structure and its usage in North America but might raise an eyebrow if it is used elsewhere ...
My next question is if a US citizen worked in a café in The UK, decided to use this form “Did you want ...?” Would British people still think it is a grammar mistake or would they let it go knowing that person is from North America through accent?
Good question. Remember that people in all English-speaking countries tend to have shaky grammar. And we tend to disagree on what's good and bad grammar.