does the premium service allow sub taks. also can you add comments on tasks ?
With Todoist Premium you can add notes to tasks, but sub-tasks and sub-projects are available for free.
To create a sub-task, enter a particular project, use the "Add task" link at the bottom and while the task input field is opened, use the arrow icons on the right side of it. Alternatively, you can use the keyboard shortcuts: Ctrl+RightArrow and Ctrl+LeftArrow to indent/unindent a task.