English has several idioms to cover general advice, "you" (particularly appropriate when intended for immediate application by a hearer), "one" (kinda pompous or disparaging) and "someone" (or even "a person"). Other languages handle the matter is other ways, similar or different. The question is, how does Lojban handle it? Prescriptively, the answer is: it's a variable, since it's general. But the issue is whether using {do} is simply wrong -- and malglico -- or is a legitimate idiom that grows out of good Lojban usage (at some small cost to logicality, as with all idioms). Personally, I'd stick with nice safe {da}, but I am not an active member of the Lojban speech community, so don't get a vote.