As the WMF-Legal project tag was added to this task, some general information to avoid wrong expectations:
Please note that public tasks in Wikimedia Phabricator are in general not a place where to expect feedback from the Legal Team of the Wikimedia Foundation due to the scope of the team and/or nature of legal topics. See the project tag description.
Please see https://meta.wikimedia.org/wiki/Legal for when and how to contact the Legal Team. Thanks!

Hi @Mike_Peel - thanks for sharing your thoughts on this. From the limited deployment we've done so far you're not the only person who's raised these concerns.

As part of T295621 we'll be making this notification on-wiki only (i.e. users won't receive an email). This was an oversight on our part - we didn't realise notifications sent both by default.

We've also prevented this notification from being sent to bot or system accounts, which means users with active bots won't be receiving notifications on those accounts.

In terms of opt-out, we didn't pursue adding a preference for this because it's a one-time notification; it seemed that it would take more work to go into preferences and turn the notification off than to simply mark it as read when received (assuming no email notification, of course). This also assumes users even know to expect it. Does that make sense or do you still have concerns about this?

Hi @Samwalton9 Thanks for the reply. I think the change to on-wiki notifications helps - in particular I think it solves the privacy policy issue ('We will send these types of emails to you only with your consent except as otherwise permitted by applicable law' from https://foundation.wikimedia.org/wiki/Privacy_policy ).

I think there should still be some sort of opt-out available in preferences that covers this type of notification, though - not specific for the Wikipedia Library, but for any other notifications of this type that the WMF might decide to send it the future.

I'm not aware of any current plans to implement other notifications like this one, but agree a preference would be helpful if any more were to be added.