Direct notifications help you stay updated with everything that's important to you, independently of configuration by other users. You are in full control of what notifications will be sent directly to you. Here is the list of situations when we can notify you:

• you have been assigned to the issue
• you have been unassigned from the issue
• you have been mentioned in an issue comment
• issue that you are assigned to has been changed
• issue that you are watching has been changed
• issue that you manually subscribed to has been changed
• ...anything missing? let us know

They are sent by @slackbot and look like these ones:

• JIRA issue is assigned/unassigned to/from you:
  
• your username is mentioned in any JIRA issue comment
  
• issue that you are assigned to has been changed
  

Configure these notifications on your personal settings page. There is a pretty granular control of what notifications will be sent.

Issue subscriptions

In the configuration page you can manage existing subscriptions - change their settings or remove them

Subscribing to an issue is possible from the issue screen. On the right side of the screen look for Slack Discussions panel and then click the Subscribe button.