Switched on the conversation view in my mail today and hovered over the twistie for the conversation. This displays a bubble message showing how to collapse the conversation. The problem is that this doesn’t go away. You’ll notice in the first screenshot that the bubble is still there even though I’ve scrolled down to a message that doesn’t have any responses.
It still displays even moving to other applications, views, and documents (it’s still showing up as a write this!). It also remains after going back to showing individual messages and clicking on the bubble. (See below)
It went away when I close my mail .