I don't agree with the law, there's no point in using emphasis to labour the point, the UK Govt advice on who it applies to is here https://www.gov.uk/government/publications/online-safety-act... and feel free to read it. As to enforcement, it's a new law so there has been none, hence no-one can speak to that, but you're right that extradition is the path and on that front if a similar law exists and agreements are in place, then for example most European countries would extradite. We don't know where the author is, but they posted on here in the morning of European time zones, and all I suggested is that they do their diligence on their personal risk as a result of laws that do claim to apply their service. No-one should dismiss the risk, the person should speak to a lawyer.