There shouldn't be any problem with copying comments from another reviews site. As far as I'm aware the comments belong to you although some sites have terms that allow them to use your reviews for their own purposes once you have posted them there. But that doesn't stop you from copying them.
As Melanie says, there are many EYB members who copy their reviews from ChowHound as well as from Cookbooker. We welcome any reviews, wherever you wrote them originally. Just remember to remove any references to other posts in the original location as that would be confusing.