Mark-Read behaviour
I think the mark-read behaviour should be the same as official client, in particular the automatic-mark-as-read is missing, right now, you always have to explicitly mark items as read (even with the setting to mark things as read when clicking to type a reply).
Official client will mark things as read automatically a couple of seconds after you enter a new channel (or the window is activated) and all the unread items are visible on the screen.