Re: wp-super-cache strategy
When viewing the member profile $bp_skip_blog_check is null. So the above does happen.
When viewing a directory $bp_skip_blog_check is true, $bp_no_status_set is null so it does status_header(200). The var $pages ($bp_path) is plugin-template.
Then it does load_template() which gets us back to the is_404() question because it extracts the $wp_query->query_vars which have no validity since we aren’t in Kansas.
Template runs and $wp_query->query_vars are showing what? That wp doesn’t know anything about this page.
var_dump($wp_query->query_vars) shows everything is empty except a few things like ‘pagename’ and ‘name’ for member theme profile in the header.
is_404() happily returns true.
status_header(200) doesn’t seem to be enough to convince wp that all is well. What would?
is_404() just does return $wp_query->is_404 which isn’t even set.