Maybe I wrong. But it is possible. I have another engine where forum module serves as comments. If somebody posts a comment the topic is created at forum authomatically.
look at the bootom of this page:
http://www.activemodules.com/active...ts-module/ there are comments which are actually forum replies. The initial first forum post is authomatically created description of the page where the first comment was posted.
it is very good and possible feature. And it is easy to modarate comments since moderators can just review forum page which is hided for all except moderators