"Enforce" yes but the point is that this fork clearly violates broader principles and conventions around respecting clearly active trademarks. Nobody is demanding a lawsuit in French court or any particular legal consequences. But it is totally valid and reasonable for an international company like Cloudflare to crack down on hosting his website: they have French customers.

Also it's really not a finder's-keeper's thing with trademarks and international borders. If someone trademarked Notepad++ in the US and released some janky port with the Notepad++ name, Don Ho could likely still win in US court. Most reasonably knowledgeable US consumers who are plausibly in the market for a Windows text editor are at least superficially familiar with "Notepad++" as the name of a well-regarded software product. I know we travel in certain circles, but there is a reason this guy wants to use "Notepad++" and not "MacnotePlus - A fork of Notepad++ for MacOS." It's a famous name.