Hi fellow blogosphere. I believe UThink Blogs have comments turned off by default (to prevent spam), so if you post on your classmate's journals you will see the message "Your comment has been received and held for approval by the blog owner." You can choose to approve comments individually -or- you can turn on comments globally.
To turn on comments for your journal:
Open your blog
In the lefthand column, click on "SETTINGS" option under configuration
Click on "feedback" (third option on top link list)
Fiddle with your options from there