(following up on my own mail just sent to this list)
For completeness sake, here is the console printout after killing jackd:
Jack: JackServer::Stop
Jack: JackThreadedDriver::Stop
Jack: JackPosixThread::Stop
ALSA: channel flush for playback failed (No such device)
Cannot stop driver
Jack: JackPosixThread::Stop
Jack: JackRequest::Notification
Jack: JackRequest::Notification kQUIT
Jack: JackSocketServerChannel::Execute : JackQuitException
Jack: JackPosixThread::ThreadHandler : exit
Jack: JackEngine::ClientNotify: no callback for notification = 15
Jack: JackEngine::ClientNotify: no callback for notification = 15
Jack: JackServer::Close
Jack: JackServerSocket::Close /dev/shm/jack_default_1000_0
Jack: JackClientSocket::Close
Jack: JackAudioDriver::Detach
Jack: JackEngine::PortUnRegister ref = 0 port_index = 1
Jack: JackEngine::PortDisconnect ref = -1 src = 1 dst = 65535
Jack: JackGraphManager::DisconnectAllOutput port_index = 1
Jack: JackConnectionManager::RemoveOutputPort ref = 0 port_index = 1
Jack: JackEngine::ClientNotify: no callback for notification = 10
Jack: JackEngine::ClientNotify: no callback for notification = 10
Jack: JackEngine::PortUnRegister ref = 0 port_index = 2
Jack: JackEngine::PortDisconnect ref = -1 src = 2 dst = 65535
Jack: JackGraphManager::DisconnectAllOutput port_index = 2
Jack: JackConnectionManager::RemoveOutputPort ref = 0 port_index = 2
Jack: JackEngine::ClientNotify: no callback for notification = 10
Jack: JackEngine::ClientNotify: no callback for notification = 10
Jack: JackEngine::PortUnRegister ref = 0 port_index = 3
Jack: JackEngine::PortDisconnect ref = -1 src = 3 dst = 65535
Jack: JackGraphManager::DisconnectAllInput port_index = 3
Jack: JackConnectionManager::RemoveInputPort ref = 0 port_index = 3
Jack: JackEngine::ClientNotify: no callback for notification = 10
Jack: JackEngine::ClientNotify: no callback for notification = 10
Jack: JackEngine::PortUnRegister ref = 0 port_index = 4
Jack: JackEngine::PortDisconnect ref = -1 src = 4 dst = 65535
Jack: JackGraphManager::DisconnectAllInput port_index = 4
Jack: JackConnectionManager::RemoveInputPort ref = 0 port_index = 4
Jack: JackEngine::ClientNotify: no callback for notification = 10
Jack: JackEngine::ClientNotify: no callback for notification = 10
Jack: JackDriver::Close
Jack: JackConnectionManager::DirectDisconnect last: ref1 = 0 ref2 = 0
Jack: JackGraphManager::DisconnectRefNum cur_index = 1 ref1 = 0 ref2 = 0
Jack: JackEngine::ClientInternalClose ref = 0
Jack: JackEngine::ClientCloseAux ref = 0
Jack: JackGraphManager::RemoveAllPorts ref = 0
Jack: JackDriver::ClientNotify ref = 0 driver = freewheel name = system notify = 1
Jack: JackPosixThread::Stop
Released audio card Audio2
audio_reservation_finish
Jack: JackDriver::Close
Jack: JackConnectionManager::DirectDisconnect last: ref1 = 1 ref2 = 1
Jack: JackGraphManager::DisconnectRefNum cur_index = 1 ref1 = 1 ref2 = 1
Jack: JackEngine::ClientInternalClose ref = 1
Jack: JackEngine::ClientCloseAux ref = 1
Jack: JackGraphManager::RemoveAllPorts ref = 1
Jack: JackEngine::Close
Jack: JackClientSocket::Close
Jack: no message buffer overruns
Jack: JackPosixThread::Stop
Jack: JackPosixThread::ThreadHandler : exit
Jack: Succeeded in unlocking 107341340 byte memory area
Jack: JackShmMem::delete size = 0 index = 0
Jack: ~JackDriver
Jack: ~JackDriver
Jack: Succeeded in unlocking 1196 byte memory area
Jack: JackShmMem::delete size = 0 index = 1
Jack: Cleaning up shared memory
Jack: Cleaning up files
Jack: Unregistering server `default'