People say "background" here, because the default assumption is HN readers have software expertise, but it's frequently unclear what else, if anything, they have here.

I do agree "background" is vague, but I generally assume the minimal threshold to say that is something like a previous career, undergraduate degree, or graduate degree in the background. I personally wouldn't say I had a background in something I was only an amateur enthusiast of.

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That being said, what on earth gives you the idea a substantial background in sociology WOULDN'T be relevant here?

Because I understand what sociology is and isn't, since I too have "a background" in sociology and urban development. As well as statistics, history and even futurology.

Appeal to authority is a bias for a reason. In this case it wasn't even that well executed.

A "background in software development" (an HR or a marketing girl in the website design sweatshop) does not give enough relevance and authority to speak about the technical details of Linux kernel. Vice versa.