There is a user in Superuser named "Rounit". This link shows a contribution of his in Superuser:

Indirect Function in Excel

Now if I try to find him in Superuser site, I first go to:

https://superuser.com/

then on left panel I click on "Users". Then I choos "All" at the right side. Then I put the name "Rounit" inside the search box and hit the key "ENTER". Nothing comes up! Can anybody explain this?