So how big does Rednote need to be to "majority stakes in media companies in the US"? I don't like this ruling at all, but it feels very American to see another looming threat and say "well, I'll just wait until it gets too big to deal with it".

It qualifies already, but I really doubt it's going to take off for many reasons. It isn't TikTok, the CCP has a much heavier hand there (ask the kids who ran into a 48 hour review period for their posts), and frankly I don't think the CCP is going to appreciate a bunch of mostly young, leftist teens sharing their ideas with Chinese people. The reaction to "Here's how you can organize a union/3D print a gun" has been hilariously predictable.