Issue

Jira Service Management (JSM) 4.18 introduced the feature described below, and which is mentioned in the JSM 4.18 release notes

Whenever a customer mentions another user in a comment from the portal, such user will be automatically added as a participant.

This new feature may introduced some unwanted behavior. For example, a customer might mention another user in a support ticket without the intention of adding this user as a participant. As a result:

• the mentioned user will be treated as a "customer" in the scope of the ticket, which might impact JSM automation rules that are configured to be executed based on the role of a user (customer vs agent role)
• this user will start receiving customer notifications from this ticket

Currently, there is no setting in the Jira UI that allows to disable this new functionality. The only way to disable this feature is to modify Jira's dark features by following the steps below

1. Navigate to <BASE_URL>/secure/admin/SiteDarkFeatures!default.jspa
2. Enter sd.customer.portal.editor.mentions.disabled in the Enable dark feature section
3. Click on Add

Suggestion

Add a new setting meant to disable this new feature/behavior either at the whole JSM application level, or at the JSM project level