[isdnmatt]

I've found numerous registry keys like "VZWSMSAssisted" and "VZWSMSAck" etc. throughout the registry, many set to "1", but when set to "0" none have effect. Maybe I'll start writing down the keys I've tried in case someone finds something I missed.

Everything was changed, then soft reset to test

HKLM\System\Inbox\Settings\VzwSmsDeliveryAck set to "1", change to "0", no effect.
HKLM\SOFTWARE\HTC\RIL\EnableVZWSMSAssisted set to "1", change to "0", no effect.
HKLM\SOFTWARE\OEM\SMS\DeliveryAck set to "1", change to "0", no effect.

I think that's all I can find for now... It sucks that the solution may be to ADD a key and that's pretty much a shot in the dark for me.