Item 1 and 2 are Under Review.
Item 3 has been Completed.
I’ll keep you posted as I hear more on this request.
-WarrenJoongi Kim commented
I have conversations longer than 100 messages often. When expanding or collapsing them causes the width of grouped messages (a post) changes to fit with the maximum width content of the visible messages. This causes the rendering engine to redo the whole layout and painting process. Also clicking the reply area changes the layout (the reply box gets bigger) and makes the UI slow.
I think we need to minimize re-layout and repainting as much as possible to get smooth and responsive UI. It would be better to fix the post/message widths to the width of conversation view. I hope next "compact professional UI" refresh resolve this issue as well.
We’re currently working on defining a compact mode experience. I will post more details when we have more to share.