WebmasterQuery

It is a good idea to let people leave their links in your blog as it gives Google the image that you have an ordinary blog even if you are just having it for the sole purpose of monetizing it. It just looks for natural but I would delete the comments that are clearly spam like "Nike replicas and more www.nikefakes.com". Now making your blog have nofollow on it is a different discussion as then people would probably not post links but I'm not entirely sure if you would get penalized, anywho best of luck!