I did figure out that I could change the portal template(s) to remove the header
Following on from that, I'd like to suggest that some reference be made somewhere to the fact that one needs to clear the cache before changes to the templates can be seen. I only discovered via a forum search. There are are least two places where I think this could be mentioned:
1) Once you've edited a template and clicked update, the "Template has been updated" message should say (something like) "Template has been updated. You will need to clear your cache in order to see the changes on your forums." (Bonus points for linking to that page of the Control Panel.)
2) The
administration guide should mention this in the paragraph about templates.