I really like the card view in Thunderbird but find it unusable in threaded mode. The issue is that card view sorts the messages in a thread in thread order but shows them as a flat list. This often puts the last message in the thread in the middle of the list and makes it impossible to find at a glance. I think, as long as the card view displays threaded messages in a flat list, it should follow the chosen sort order, not the thread order.