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The "Add notes" permission lets users add notes without editing the issue. But whenever a user is allowed to edit an issue, he is allowed to add notes by design.
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_But whenever a user is allowed to edit an issue, he is allowed to add notes *by design*._

IMHO this is not a good design decision:

* All systems I know (SBM, JIRA, ...) behave in another way: the feature of adding notes or attachments is something separate from the ticket itself (that others do it is a poor argument :-) I know)
* The expectation of removing the "Add note" check box in the permissions is that there is no possibility to add notes. Still allowing this because of edit rights on the issue undermines this and makes it impossible to realize that use case. Rights for editing issues should not be include adding notes.

Or put more simply, why restrict the amount of possible use cases artificially?

I consider the "Add Notes" behavior should be changed too.

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