That's not the example that either I or the article are considering. We are talking about getting banned from the instance you are federating with. You can't

That's not the example that either I or the article are considering. We are talking about getting banned from the instance you are federating with. You can't get booted off of reddit for violating rules specific to a subreddit. But with Mastodon, the initial choice of instance to join determines all future Mastodon behavior.