After using Phabricator for a while, some members of my team suggested that it would be helpful if a "Submit" button appeared as soon as a comment was added to a revision, to allow them to quickly submit without having to scroll to the bottom of the page.
This isn't a particularly serious problem; turning on comment panel haunting is a reasonable workaround. But I can see how having a smaller, less intrusive Submit button automatically appear would be a bit nicer.