Question:

When Approving or Rejecting an Event, the comment of Submit for approval requests is stored in the Event History object and Salesforce Approve History object in CRM. But, the comment of the approval or reject is stored in the Event History object.

Is this by design?

Answer:

This is currently an expected behavior.  The user can see the Approval or Rejection comment from the Event History object. 

Related Documentation:

N/A