Iiiinteresting, Mastodon changed the behavior for what happens when you are viewing the user profile on a remote server and hit "follow". Instead of the often-not-working "remote follow" action, you now get this modal that says "please copy/paste this into your client and hit follow"
@darius I assume this would break the "simplified federation" Firefox add-on I've been using: https://github.com/rugk/mastodon-simplified-federation
It works well, but having to install software to follow people may be a non-starter for most.