Instantbird 0.2 uses the multitouch feature of Macbook touchpads in conversation windows:

• Pinch in or out 2 fingers to change the zoom level.
• Swipe up (3 fingers) to scroll to the top of the conversation, down to scroll to the last message. This saves time when looking for an old messages in the conversation (for example, using the Find feature) and then going back to the display of the most recent messages.
• Twist left or right to select the tab at the left or right of the currently selected tab.
• Swipe left or right (3 fingers) to change the selected tab to the previously selected tab. This gesture is probably the most useful one: it’s very convenient when reading quickly a message in a newly opened tab and then going back to the conversation tab where an active conversation is occurring, or when actively participating in 2 discussions and repeatedly switching between 2 tabs.