I see a user "distributed" on my cluster - who is this user?
The "distributed user" is a regular user who happens to be named "distributed". It is used for communications between nodes within the cluster.
All Singlestore nodes (are supposed to) have a user named 'distributed'. This is the user that Singlestore uses for all connections between nodes in the cluster (aggregator-to-leaf connections for queries, leaf-to-leaf connections for reshuffles/broadcasts, heartbeat connections, etc.). It is intended to be an "internal" user with which an administrator will never need to interact directly.
Managing or hardening this user (trying to change its password manually, changing its permissions, etc.) is not recommended, and attempting to do so might damage the cluster; hence it is advised against manipulating this user.