How to make comments internal
There are limited paths to making comments internal, this article explains them.
See also https://support.atlassian.com/jira-service-management-cloud/docs/what-are-user-types-and-roles/
Commenting as an Agent
JEMHC gives control over whether comments are public or internal when they reply by Email. See:
Profile > JSM Project Mapping > Issue > Comment > Service Project Comment Mode
Commenting as a Service Desk Team role member
If you are a member of the JSM Project specific Service Desk Team role, then such parties are deemed Collaborators, who's comments are always internal (exception is where they are the reporter/ are included as a request participant, see below). Only Agents can make public comments to Customers (JSM licensing is based on Agents).
Collaborators and Request Participants
If a sender is included in the JSM Request Participants, they are treated as any other Request Participant. All comments by Request Participants are public except if they are in the TEAM role in which case they will always make internal comments!
Only when the sender is not in the JSM Request Participants field would the be treated as Collaborators and therefore have internal comments.
TEST Access when granting application access
Be sure you create a test user and validate access granted to avoid unexpectedly opening your entire support system to 3rd parties…
If you create a user and grant them an application group (eg Software) then the user can login to your instance and browse all the support issues (perhaps a privacy issue!)
On the flipside, a user without any application group will not be able to login to the system (Software/JSM) so cannot browse any issues and can can only use the Portal. Such users, not being Request Participants cannot see any issues, including the related issues they commented upon.
Example
In the example above:
made by the JSM Agent who also created the issue, JEMHC is set to create internal comments for Agents.
made by a user in the Service Desk Team role when they have a Software license
made by a user in the Service Desk Team role when they do not have a Software license, its attributed to the JEMHC app user (ignore variances in the App user name, it seems to change over time)
made by a user in the Issue Request Participants field and the Service Desk Team role regardless of whether they do/do not have a Software license