This is a bit strange, but to shorten a story:
I was a user of the Elementary OS Stack Exchange (User 3).
I removed this account because I disagreed with the community moderation decisions. It was removed (in fact, it was removed manually).
This account became "User3" on the site, with no logo and the grey user background on posts etc. Today, there is no account on the site with the id 3.
I rejoined the site with my "Tim" account to ask a question (a while ago), and became User 2926. I remember seeing a deleted account with the name "User 3" and no icon (i.e. After I signed up again my deleted account was still deleted).
Today, I got a reputation change from a question asked by User 3. I'm not sure if I answered this before User 3 was deleted or after User 2926 was created.
When I visit User 2926 on the Elementary OS site, it has a geometric Gravatar, not my elephant and the name "User 3".
The reputation for User 2926 is way below what User 3 had.
It would appear that my name and my icon has changed on Elementary OS to be "User 3" and the geometric gravatar. Why this has happened, I'm not sure.