With machine learning they might only need to know your pasting habits and what function names you use most commonly, maybe a bit of information about how fast your type and this will be enough information to identify you based on your behaviour.

Search engines are recording really detailed information as you type, as you browse other websites using their invasive trojan-like analytics. With this data you can probably identify anonymous users from their behaviour (even if the ipv4 address is "encrypted" hah). All it takes is for data from one company to end up at another company and I believe this happens very often.

I think the problem is that you need less and less information to personally identify someone as you have more data. We are not intelligent enough to know what data is identifying or not so therefore the only option we have is to stop giving out our data.