Let say if you have masked your IP and browser fingerprint.

You can still be matched with a corresponding usernames based on your writing style.

Here is an experiment conducted by a hn user on hn data: https://news.ycombinator.com/item?id=33755016

This site lets you put in a username and get the users with the most
similar writing style to that user. It confirmed several users who I
suspected were alts and after informally asking around has identified
abandoned accounts of people I know from many years ago. I made this
site mostly to show how easy this is and how it can erode online
privacy. If some guy with a little bit of Python, and $8 to rent a
decent dedicated server for a day can make this, imagine what a company
with millions of dollars and a couple dozen PhD linguists could do

On the same day, he closed the site due to privacy concerns (Because it was working too well)