Currently no indicator exists for the customer added comments or Alerts or subscription in the tableau server.
indicator number display would be insightful so the users can easily identify that there are comments, alerts or subscriptions associated with the dashboards.
This indicator should display number of comments or alerts or subscription added.
This functionality will alert the users visiting the dashboard and encourage them to view comments or alerts added by other users.
Without the indicators display their are no flags for the users to go and view the comments or alerts and get further detailed information.
If you cannot add the number of comments at least add some flag to review comments or Alerts.