Similar to Ticket Detail, Comments tab section is divided into several parts. The top most part contains source icon, task Subject, link to parent ticket, total time spent (Note: displayed only if comment timer is enabled), Created, Updated (User and time) and Stage. Below those is the Description.
Below this part is the comment box displayed where you can add comments for the task. Below the comment box, existing comments are displayed. Functions are similar to comment section of Ticket Detail, see section Ticket Comments.
Note that for a task there is no useable difference between Internal and Public comments. A task has no Requester (End User) as recipient of Public comments, so in fact all comments are Internal for tasks.