look at some other links that have been left on the site. Check the source code of the page, and see if the other comments that contain links have a rel="nofollow" in them. Or you could just leave a comment yourself, and check the source. Not that hard. Hope that answers your question man.
You can also get an extension for firefox that highlights nofollow links. But most blogs are nofollow by default anyways. Unless they use the Top Commentators plugin