[LewisJEllis]

If we're going to drop assumptions, then let's remember that context matters and not everyone on HN is a computer scientist or familiar with communicating sequential processes.

If the context is not "computer science" but instead "web technologies" or "computer security," then CSP most certainly stands for "Content Security Policy." It's perfectly possible to know one meaning but not the other; as someone with a CS degree working in internet security, I'd heard of communicating sequential processes once or twice before, but they were at the back of my mind in comparison to content security policies.

But of course, since not everyone on HN works in security or on web technologies, it would've been more "widely understood by others" if the title expanded to say "Content Security Policy" instead.