What separates comments from regular posts is that they do not undergo review. Whenever someone posts an answer (or a question), it is shown on the front page. When you edit it, same thing. First posts from new users are placed in special review queues too. This is all done as a kind of quality control measure.
Comments cannot be reviewed that way. Even if it was technically possible, it just wouldn't scale. There would be too much to review.
New users might not understand how the system here works. They'd litter the place with "I have the same problem" comments (they do it in answers, too), they'd insult people, or some of the more nasty folks would post spam where it's very hard to catch.
We really want users to be trusted members of the community before they're able to leave comments everywhere. Enabling everyone to comment would certainly increase the amount of noise that we so desperately try to avoid.
I would really encourage you, as a new user without commenting privileges, to focus on answering questions first. The kind of question that does not need to be clarified any further. Then you'll be at 50 rep in no time.