Salesforce comments within Jira can be filtered by administrators using hashtags, (e. g. #jira, #jira-servicedesk, #sfjc).
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Add hashtag filters in Jira
Go to Settings > Apps, and then in the sidebar, under SalesforceCONNECTOR FOR SALESFORCE, choose Connections.
Choose the connection you wish to configure, then click Configure.
On the Connection Configuration screen, scroll down until you see the Comment Tag Filter section.
Administrators can enter the hashtags that they want to use to filter comments from Salesforce.
Info Tags must be preceded by a "#" and separated by a space.
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View filtered comments in Jira
Filtered comments will appear in a Jira Issue based on the Comment Privacy settings plus what hashtags were configured by the administrator (see above).
In Salesforce, to add a hashtag to a Case Comment, simply edit the comment and add the hashtag anywhere in the comment: