The case sensitivity of the

/rest/api/2/issue/{issueIdOrKey}/comment (POST) 

call seems to have changed during the update to Jira 6.2.

Prior to the update we were able to pass through:

{'body': 'test', 'visibility': {'type': 'role', 'value': 'staff'}}

The role is actually "Staff", but it still worked. Post-update, this now results in a 500 error

{"errorMessages":["Internal server error"],"errors":{}}

Not a major concern, but this has changed the functionality of the API without changing the version.