To run the Comments - By Type report:
  1. Go to Reports > View All > Category > Comments > Comments Reports
  2. Select Run for the Comments - By Type report
  3. Select your desired filter options
  4. Click Generate Report
  5. If you get this message in the results, make sure you have the Comments Manager role  
 
To grant access to the Comments Manager role:
  1. Go to Core > Users/Access > Profile > Manage Roles
  2. Click on Comments Manager
  3. Click on Members
  4. Click Add
  5. Search for the user
  6. Click the double arrows '>>' to move them to Added Users
  7. Click Save & Exit
Alternatively you can clone the Comments Manager Role; see How do I create a clone of a role?