This is good, but the point here is not to write a thorough test.  The point is to write the simplest possible test to get them started.  One where they can understand every API call quickly.

Also, good test cases test only one thing.  You are testing permissions, display settings, enumeration of all possibile comments, etc.

This case should look like:
* Login as a user who is allowed to (authenticated)
* Post the comment
* Get the comment ID from the URL
* Do a lookup in the DB using comment_load() to make sure it is there.