Rounit is an unregistered user. You can see this in the user profile.

Unregistered users are no listed in the [Users][1] lists.

References

- https://meta.stackexchange.com/q/49764/289691
- https://meta.stackexchange.com/q/134415/289691

Related

- https://meta.stackexchange.com/q/192191/289691

  [1]: https://superuser.com/users