When the status of a task with a parent gets updated, I get two notifications:
user changed the status of T123: XXX from "Open" to "Needs info"
user changed the status of T123: XXX, a subtasktask of T456: YYY, from "Open" to "Needs info"
I like the word "subtasktask", but I think it's a typo.
Also I like the idea of the second notification but it makes the first one redundant if I'm subscribed to both. If that makes sense, I can create another task for that.
D17373 should fix the typo.
Sending you only one of the notifications is more complicated. Users may be subscribed to only one of the tasks, in which case they should receive separate halves of the notification. For technical reasons, it is also currently difficult for us to send either notification to only users who didn't receive the other one (the parts of the code which send the notifications don't really know about one another).
I don't expect to pursue this until the next major update to feed/notifications, which would give us a better opportunity to tackle this and some related issues (T9284 wants more of this general sort of two-sided notifications, T11432 discusses aggregating similar stories/notifications in the comments, and T5891 does as well), probably mostly through display-time aggregation rather than changing which notifications we emit. Although it's not directly related, I would guess that T10448 will also happen first.
Thank you for the very thorough reply.
That's not a big deal and it certainly can wait!