idea number 3: Unsubscribing from e-mail-notifications
A the moment an author of a posting can not unsubscribe from a notification when she/he has no access to editing the posting. The user should be able to disable the subscription. This is a request made by Magma. See therefore also Github issue #331.
Would it be enough to provide an unsubscribing link in the e-mail-notification? An addition with a higher effort would be to provide a page with a list of subscriptions in the users profile (was requested in that posting). I know, the best would be to have both ways but I want to limit the effort to the necessary.
IMHO it's worth to implement the link in the e-mail first and to add the page afterwards. With the link and it's processing we have the infrastructure to get such a page working.
Trenne niemals Müll, denn er hat nur eine Silbe!