I only ask personal questions when I am genuinely interested and caring; when I am trying to create a friendly relationship with the person. I have no ulterior motive, ever. If I don't particularly care I won't ask.
Asking what someone is doing for the week-end is, to me, a polite way to make small talk. I would never compare or judge.
If I asked someone a question and they came back at me with, "I'd rather not talk about it" I would take that to mean they don't want to invite me into their life. I would most likely ignore the person after that, because my initial intention would have been friendly.
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