I'm not (yet) an SF user, so I got here out of curiosity after we migrated a question from SO to SF. I was surprised to see that, on the main page, some questions were highlighted as if I had any "interesting tags" defined, but I didn't even have an account.

This is in mobile version, not sure if it's relevant.

P.S. I can't reproduce it now, after I created an account, even when logging out.