I feel this is little unnatural I appreciate allowing users to answer without any minimum reputation but why restricting them from commenting.By restricting them to comment with limiting reputation to 50 the new users using answers to express their views and the next process will be deleting of that answers I hope there should be no limit for commenting too so that at least some burden on moderators will be reduced.Hoping SE developer will respond in positive way.
Comments play a very different role than answers.
Comments are used for clarification, and constructive criticism. Many new users come from forums, and other websites where comments are useful for things like "thanks." As such, it's useful to restrict them to only users who have a little experience with the system. In addition to that, comments can be difficult to effectively moderate, due to quantity, if nothing else. If all users could leave comments, we'd run a strong risk for spam.
Answers, on the other hand, are very pivotal to the system. Without answers, this whole system would be pretty useless. If we limited answering to higher rep, that would undermine much of it. Many top answerers across the network have asked very few, if any, questions. By blocking those users out, we'd lose a ton of positive content.
It's true that this system leads some new users to use answers inappropriately, but I suspect that's a very small percentage of the content that would have to be deleted if we opened commenting up to everyone. At least the word "answer" has a relevant meaning, and consequently hints to some users what should be put there. "Comments" might mean different things to different people, so it's good to make sure people are used to them before granting full access.
There's a very good reason for why these privileges are attained at different reputation levels, and I definitely would not like to see them changed.
This is a Q&A first. Comments are secondary to everything else. They not only can be deleted for whatever reason, but are normally hidden when they clutter. They are worthless. Answers, in comparision, always gets the spotlight, also, there are just so many definitive scenarios that would warant the answer to be deleted. They have worth.
Comments are just for "clarification", answers "answers" the question. You first have to know what is answerable as is to later know what needs further clarification.