Jump ducts are extremely rare around here. Transom vents over doors are very common around here. And yup, everyone can hear everything going on in the other rooms. 
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Not sure where it would make more sense to have attic penetrations than using the high/low wall cavity instead.
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I have done hundreds of verification inspections in Oregon for a regional ‘green’ program over the last 8 years. The program specifies no more than a 8 pascal pressure differential between the bedroom and the open part of the house where, normally, the return is located. (Side note, some other programs I’ve looked at allow a differential of 3 pascals or less.) Jumper ducts are used to satisfy this requirement in many cases. Door undercuts will sometimes satisfy this, but, as many have remarked on, at the cost of privacy. I have sometimes had to red-tag them due to not meeting this requirement, and consulted with the HVAC contractor to install larger ducts due to very high supply into a master suite with more than 2 supply registers.
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