As a student, you have the ability to choose if you write a comment anonymously or not. This is designed so you can better develop your confidence in getting involved in the class-based discussion online if you don't have confidence in what you're contributing.
When writing a comment, you'll see a small icon on the bottom right of the commenting pane. Click this to decide if you write a comment anonymously or not.
If you write anonymous comments on a single resource, you will be given an anonymous avatar. This is a unique Identifier that will follow you through this resource. For each resource, you will have a different anonymous avatar.
If you have written a comment anonymously, but want to change the comment to show your name, you'll need to delete the comment and re-write it again.