The purpose of the swearword "fuck" is to signal that you are passionate and emotionally unrestrained about something, with a slight underlying threat of violence. Can someone explain why that is appropriate on this well crafted site?
Sure it is. It's "incredible versatile" if you want to express how angry you are about something, because you can basically use it as either a drop in replacement or an intensifier for any word you want, but the common meaning is to express your emotional state. Look at the examples on wiktionary, for example.
As for "what the fuck" being a well established idiom - I guess that depends on your demographic, but I don't see it showing up much in the respectable media, or in academic papers.
Anger is not the only use case for the word "fuck", nor is expressing an emotional state. Really, there's a fuckload of other fucking examples; enough to make one tired as fuck just fucking thinking about them, so I won't enumerate them here (those readers who give a fuck can now exclaim "thank fuck!").
"Respectable" media are beholden to their advertisers, who in turn are concerned that specific demographics might be scandalised by certain words and affect their bottom line. I don't think HN or much of the internet fits into this category.
Academic papers are an interesting case. I suspect their avoidance of the word fuck is a combination of their inherited sense of propriety and the fact that such an ambiguous word as "fuck" rarely has a place in scientific writing.