Yes, I should clarify I was not intending to ring the alarm bell as if Hacker News is directly under attack. Most likely HN is completely not subject to Australian jurisdiction, and even if it was, there's no money to squeeze from HN anyhow. I just meant it as an exemplar of a type of site that could be affected.
First, Y Combinator has to be in Australia. I don't know if funding a company there would be enough; suspect not. I don't know whether they have funded an Australian company.
And I'm not going to look, because secondly, even if Australia did somehow get its hooks in to HN to some significant degree, and there was no escape, Y Combinator would simply shut down HN. It's nice enough of them to run it as it is, but expecting them to play by these rules to do it is unreasonable. If they were feeling particularly friendly they might spin it off or something. (Turning it into a subscription service is probably feasible at this point, for instance.) Unlike Google or Facebook, HN is not their core business, and shutting off at this point could even be a net gain for quite a few years. The rep gain that HN afforded them is mostly realized now.
There's no way for Australia to squeeze Y Combinator through HN.