The .htaccess file shipped with phpbb contains

#

1. The following 3 lines will rewrite URLs passed through the front controller
2. to not require app.php in the actual URL. In other words, a controller is
3. by default accessed at /app.php/my/controller, but can also be accessed at
4. /my/controller
   #
   RewriteCond % {REQUEST_FILENAME} !-f
   RewriteCond %{REQUEST_FILENAME}

   !-d
   RewriteRule ^(.*)$ app.php [QSA,L]

The lighttpd.sample.conf file does not have an example of using mod_rewrite to achieve the same thing. Might be beneficial to add an example to save people having to figure how how to translate the apache syntax into lighttpd mod_rewrite configuration.

Just makes the plugins that go via app.php appear a bit nicer when it's configured correctly. (i.e the board rules plugin)

Not a major issue. Just something to save others in the future some hassle.