The cached post attachment took me to an intermediate link.  When I used "copy link" I was able to insert it into a placemark and get a workable downlink.  The real question is what will happen when the revised file is attached to the post.  It's still a question of the underlying structure of the database.  Will it be like the UBB forum where the file was created, and a link went to whatever file was attached to the post, through multiple revisions?  Or will it be like the last incarnation of UBB, where the index changed every time a file was replaced, and so all links to it were broken?