Inconsistency with how Jira notifications are sent to users treated as Customers when they are mentioned in a ticket

Issue description

When a Jira user is added as participant of a Service Desk request, this user should be treated as a customer and therefore should not be able to receive any Jira Core notification (notifications configured in the Notification Scheme, and meant for agent users).

This behavior:

• is described in the documentation Managing service desk notifications
• is addressed in the feature request JSDSERVER-6248

There are 2 scenarios where the notification mechanism is not consistent:

• Scenario 1: if a user is a participant of a Service Desk request and mentioned in an internal comment, this user won't receive a JIRA Core notification from this comment (expected behavior)
• Scenario 2: if a user is both a participant and a watcher of the ticket and mentioned in an internal comment, then this user will receive a Jira Core notification from this comment (unexpected behavior)

The inconsistency between these 2 scenarios does not seem to be intentional therefore is a bug.

Expected behavior

We would expected both scenarios to lead to the same result: in both cases, the user should not receive any notification from an internal comment, since this user should be treated as a customer.

Therefore, the scenario 1 is correct (based on the design), but not the scenario 2.