No this is not a subscription based website. You need to have a certain reputation for posting comments. This is simply to ensure the quality of the site.
As @DavidPostill suggested. Please refer to the help section:
What is reputation? How do I earn (and lose) it?
Why do I need 50 reputation to comment? What can I do instead?
Posted this as an answer in the light of making sure everyone else interested notices it.
