Issue Level
By using Issue Tools you can configure Channel Notifications for given issue and specify which events should trigger them (Fig.1). You can select any already existing Slack channel that you have access to (Fig.3) or create a new one (Fig.2). There can be more than one channel linked to every issue, for example, with different set of events.
Threading for Issue Notifications
When configuring issue-level channel links, you can enable threading by checking the "Use threading" option. This will group all notifications for this specific issue into a single thread, making it easier to follow the issue's history in Slack without cluttering the channel. Than option is very handy especially for channels that are not dedicated just for one particular issue.
Fig.1 Choosing events that should trigger notification on issue level channel configuration
Fig.2 Create Slack channel dialog
Fig.3 Choose Slack channel dialog