Since you posted your question in this section, I think we should point to the ‘non-standard’ dimension of declaratives when used as questions. “You smoke?” is certainly not a very elegant or widespread way of asking a question.
If you stretched yourself, you could possibly think of a pragmatic context, but it’s definitely not standard English.
I’ve never heard that “You smoke?”, or similar, even if not what you call elegant, is non-standard. It is conversational, but I wouldn’t call it non-standard, with or without the quotes. Rising declaratives are used when one is skeptical about something and/or where one is partial and informed, i.e. they are not neutral questions and express bias. Also, such question need to be preceded by a relevant context. I would say constraints on use have nothing to do the with standard vs. non-standard argument.
You said “one of the rare occasions when…”. What did you mean by that, Ralf?
I don’t see how the falling declarative is a question at all, in those contexts.
I agree that the rising declarative as a question is VERY common.
It’s time? (Can be stated quite mildly - as in, when your boss sticks his head in your door and you both are attending the same meeting.)
He’s here? (Can be stated in a state of surprise.)
You went to the pool? (Can be said in irritation, surprise, or mildness. (Guess what we did today? Eyeing the damp towels on the railing, you reply, “You went to the pool?”))
It seems as if all your endless discussions about ‘standard English’ have been in vain. Or they were simply based on the erroneous assumption that standard English is not “a term generally applied to a form of the English language that is thought to be normative for educated users”, but something else.