If someone can please clarify, I don't get the minimum reputation of 50 required to comment on someone else's answer or question. This is simply too high for new users. I have lost track of about 10-20 questions/answers which I wanted to comment (with a comment as simple as 'please cite sources') - which I can no way remember and go back to do after my reputation has gone up.
It's not just Hinduism.SE is having such a rule, its the same across StackExchange network. Coming to your question that why such a rule is because new users tend to chat is because we want don't want spam from new users.
It might happen that few people can make fake accounts and start spamming across the site which is not only bad for the website but it will be tough for the users and moderators to control and keep a watch for that all the time.
Indeed we may lose some valuable information a new user might want to contribute in a comment but chances of this is too low. It's like 1 in 10 comments might be useful.
Coming to the second part of your question which says I have lost track of about 10-20 questions/answers which I wanted to comment so for this we do provide a feature which is called "Mark as Favorite" by clicking on the star besides the question. This will not only remind you for commenting but you will also get notifications for whatever activity is carried on that question.
I hope this solves your doubt. Also you have 51 reputation now so happy commenting.