Insightly Classic is the old version of Insightly. It's not available to new accounts. Users on Insightly Classic can switch over to the latest version.
When an Insightly administrator adds a new user, an Insightly contact is created for that user. But system users have special contact records.
When we look at one of these contacts, there's a red ribbon with the message: "This contact is an Insightly user so permissions and actions are limited."
These contacts can only be deleted by Insightly administrators when the user is deleted from the System Settings page, and they cannot be cloned.
If you are syncing contacts to Google, these system users will not sync because they already exist in your G Suite contacts directory.