The JIRA Toolkit plugin has a custom field for this purpose. If you're attempting to get this data in field form this is likely your only non-custom option. JIRA Toolkit available for free for JIRA Server and JIRA Cloud.
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The custom field is of type Participants Field.
It's my belief that this only includes Assignee, Reporter, and Commentors though, so I am not sure if users triggering the Issue Update event will be added to this. Good luck.
Look at the issue history, it contains a full history (The activity can lose older events)
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If you click on Activity tab, you'll see all the changes on the issue, but if you're asking for just a list of the users, I don't know. Maybe use the API and get the expanded data, using a script to grab the users.
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