[pvonk]

I would hypothesize that an action due in the future and belonging to a project this is overdue should raise a red flag. Something is possibly wrong. If the "grouped by DUE" were to drop the action in some future bin, it may be missed. If it shows up in "past due" then the user would be alerted and he could then decide if there's a date mistake or not.

I'd rather have some strange situation show up as abnormal in some way (so I can then determine whether I've made a mistake or whether the project due date needs updating) than have it appear as normal.