As you write a comment in a task's comment box, your comment is automatically saved. The draft of your comment will appear in the task's action feed. It is displayed in a separate block and looks different from other comments:
Once you save your draft as a comment, the draft will automatically disappear. If you accidentally close the browser you're working in, or if you lose Internet connection or electricity, your draft will be saved in the action feed. You can return to a draft at any time, edit it, and then save it as a comment, at which point it will become visible to all other task participants.