This is quite a slippery slope. If I host a website in one country, I do not necessarily care where people access my website from. It is not like I actively provide a service to them - they just use internet (decentralised network) to access it. What if I publish a newspaper here, someone takes it where the contents are illegal, am I accountable?
Mr Capel said: "We have been clear that exiting the UK does not allow an organisation to avoid responsibility for any prior infringement of data protection law, and our investigation remains ongoing."
When read in context, it's obvious the statement quoted in the HN conmment refers to only to accountability for "prior infringement", i.e., acts committed before withdrawing services in the UK