But it's the non-government entities you really need to be worried about. There are plenty of brokers buying up this data, making up assertions/predictions about the data, then selling it along downstream to secondary vendors who just blindly accept the data as true.

These are how people online get doxxed. It's not the government or FBI, it's these brokers who mine/buy data from sites/credit bureaus/local governments, link them across various social media, then build out profiles of individuals that they then sell to anyone with a big enough check book.

I've looked into these vendors before and their profiles on people are often wrong on several dimensions. So you don't want to do anything that's going to increase their ability to map you across the internet, because that's just going to improve their ability to identify you, while still selling lies about your personality.