It is possible to configure the visibility for the leaderboard.

Navigate to the Kudos Skill using the web app navigation bar, then click on "Skill Settings".

Find the "Leaderboard visibility" section and select one of the options:

If the leaderboard visibility is restricted for a user, that user then won't be able to see a leaderboard in the web application, neither query it from the chat bot with the "kudos leaderaboard" command.