how I can enable all visitors to my site can post comments to the products without having to register?
I have installed the version 2.0.14
Go to Configuration > Configuration > Shop Front tab, and then select the correct radio-button on the bottom right of the page - Shopper Review/Rating section
That means that those who wish to comment have to register, and I want visitors can comment without registering, I want something like this
http://tuplazaonline.com/centrocomercial/index.php/concepto
You can disable the VM rating and comments and try to integrate a social media commenting extension like Disqus to your product pages. I have not tested this but I cant think of any other way.