This is a bug just to get a little more consistency in the interaction between the thread and message panes. If you're not running with "Remember last selected message" it's been the case, for a while, that on selecting a new folder, the thread pane only has a 'current' marker, not a selection, with no message in the message pane. When you select a message, it's loaded in message pane. When you select two messages, the message pane is cleared. If you delete one of the selected messages, the selection reverts to one message and that message is loaded. The model appears to be that, if one message is selected, the message pane should show it, otherwise it should be empty. But it's possible to revert from one-selected to none-selected by using Ctrl+Click or Ctrl+Space. When this occurs, the loaded message remains in the 3-pane. So, steps to reproduce are easy: 1) Open a 3-pane with open Message Pane 2) Select a message 3) Ctrl+Click on the message, or type Ctrl+Space: selection removed Actual results: 3) message pane continues to show deselected message Expected results: 3) message pane should clear

FYI this bug predates Mozilla 1.6