I only just thought of this. I have the same cartoon-y profile pic from a foreign TV show on a bunch of my accounts, I wonder if its unique enough and worth tracking.
Anecdotally, yes. I know that the similarities in profile and avatar photos as well as signature lines on web forums have been used as evidence to link digital profiles together. This linkage then allows warrant level evidence to be used to subpoena the other sites for all user details. Another one that is much harder to hide is writing style. People have a relatively unique way of writing that is often enough to link data. Even when the user name, ip addresses, and everything else is different.
I’m blanking on specifics but I know I’ve seen a few examples of “dark web” criminals being narrowed in on by means of analyzing their writing styles and comparing them to other accounts. I want to say this played into Robert Ulbricht (the main guy behind the original Silk Road) being arrested