Hi max,
Yes, you are right.. there are a couple of other details to solve with this. For example, task B (in my opinion) should also display the fact that it is a subtask of task A, which could be somewhere else in the view - or not displayed at all, if it doesn't meet the filter conditions.
The same problem happens when grouping by "assigned to", for example. It's sort of haunting us and we haven't reached any solid conclusions yet as to how to handle this,, we also have some code design issues to consider with the fact that, when fixed, tasks could probably appear in two or more groups at the same time.
If you have any ideas or suggestions in the meantime, they will be always welcome...