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It wouldn't be appropriate to ask such questions in comments, mainly because comments are meant to be focused on improving or clarifying questions and answers, not for general chit-chat. There's a "too chatty" flag that can be raised on comments, and questions like that would probably be flagged that way. Asking such things in questions and answers is also out, of course.
You could ask such questions in Chat. That would be fine according to the site's rules. Some people might answer, others might not want to answer, others might be offended or annoyed. Just like any social interaction, there's no way to know in advance how someone will react. Also, some users never participate in Chat at all.
If you click a user's name, you can see their profile. Some people include their contact info in their profile. If so, you could contact them directly (via email, Facebook, Twitter, etc). Again, some people might not mind answering questions like this, others might get annoyed.