I have already filed this bug before, and it was marked as a duplicate, but the problem still exists in RC7. I'm not sure if you are planning to fix it at a later date, or if you think it was already fixed, but the issue is still present as of RC7. I have even tested it on the official phpbb forums on 10-16-2007 and am able to duplicate the issue there too.
The problem is that the last link in a post (and the post preview) is not underlined. See this link for my test: http://www.phpbb.com/community/viewtopic.php?f=26&t=585564&p=3225751#p3225751
Also see the attachments.