I ran into this problem with my directory which I do use php redirct for counting outbound hits and ranking the site according to that. So I created 4 separate pages for each link that was added to insure they had proper outbound links. The extra pages were user reviews, site profile ( example profile page: http://www.freepokerleague.com/viewlinkdetails-542-Casino-Affiliate-Programs.html ) and so on. On each of these pages I give a h2 link to the actual domain. While this is a little further down than an outbound link in the actual listings ( example listing page: http://www.freepokerleague.com/link-5.html ) I reason that at least I give the outbound link and optimize a good situation for the submitted site and my listing for the words in their domain name. I never require a link back for a directory listing.