As someone trying to flag a long thread it’s painful to scroll through all posts to get to the Bookmark/Share/Flag/Reply buttons at the bottom.
Reply and Notifications are currently available in the right sidebar at all times while scrolling through the thread, which is nice.
I would have Reply and a (dot-dot-dot) Overflow icon, which expands into Bookmark/Share/Flag/Notification icons.
Also the Notification icon should be a bell.