Can't they aggregate and sell your Lemmy activity data without federating with your sever? It's all in the public Internet.
I guess it won't be that useful if they have no way of tracking you. But, I don't think federation makes it easier to track users. Do sever admins get ip addresses of every user on a server they federate with?
I'm not convinced. There's already plenty of choices for chrome reskins. I'd rather they make their search engine better. Maybe get independence from bing.