The leaderboard ranks learners by XP earned.
What other people can see
Your display name, your avatar and your score. Nothing else — not your email address, not your answers, not what you wrote in an exercise.
Changing your display name or avatar
Open your profile and edit them there. The change applies immediately, on the leaderboard and on any certificate you hold.
If you would rather not appear
Set a display name that is not your real name. Anything reasonable is fine.
What the ranking means
It measures consistency, not ability. Somebody above you has finished more lessons; that is the whole claim. It is not a measure of how well anyone understood the material, and treating it as one would be reading more into a number than it holds.
Keeping it civil
Display names are visible to other learners. We will change a name that is abusive, impersonates somebody, or is used to advertise.