Hi @MC
By default, comments are allowed for each security role. But you can disable comments individually by editing the tasks in your role assignment.
For example, my item-level role is "Content Manager", and when I uncheck "Comment on reports" in the task, then when I view the report, the "Comments" button disappears.
For more details, you can refer to these links:
https://learn.microsoft.com/en-us/power-bi/report-server/add-comments#permissions
Best regards,
Aniya