Don't Open Thread Unless I Click Specifically On The Triangle
Right now when you click anywhere on a closed thread, it opens the thread. But you can only close the thread by clicking on the triangle. I would prefer it that it only opens the thread when I click on the triangle and instead just show me the most recent message when I click anywhere else on the closed thread.
Already supported in Preferences > Reading > Conversations (as someone mentioned in the comments :)
Jan Lunddal Larsen commented
You can set that in Preferences > Reading > Conversations