As a workaround, you can use a dashboard:
1 open Dashboard
2 Add Gadget Activitiy Stream
3 Add a global filter: Project is XY
4 Add a global filter: User is (username)
5 Below the Global Filter, klick JIRA - Add Filter: Activity is Comment
6 Set "limit to 99 items"
You now have the comments as an activity stream.
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