For people still looking for an easy solution to this issue, I found a simple solution.
I wanted my blog categories to use excepts but when that setting is turned on, the root forum page does not display because it is truncated as described above.
So I turned excepts off so that the forum displayed correctly and then to make the the rest of my site use excepts, I installed the plug in “posts in page”. Then I created new pages with the shortcode from the plugin to create new static pages for my posts to display in excerpts. I updated my menus and widgets to display links to the new pages so that site visitors can easily browse the posts by seeing excerpts. Plus I did not have to hard code the forum or theme.
