“ESPECIALLY INSANE.” “Drastic.” “Noisy and provocative.” These are just a few of the words used by tax experts—normally an even-keeled bunch—to describe Donald Trump’s threat to hit foreigners with punitive tax rates depending on the policies implemented by their governments. It is a sign of how the potential global economic damage from Mr Trump’s return to the White House goes beyond trade and tariffs. Indeed, tax disputes may end up being even more contentious.