simple answer: not all mod_chromes are rendering the modsuffix:
see this file
joomla-root/templates/rt_camber/html/modules.php
only the mod_chromes with<?php echo $params->get('moduleclass_sfx'); ?>
in it render it.
Wich mod_chrome is used can be checked in the index.php of your template.
Just as a code example from the index.php ...<?php echo $gantry->displayModules('navigation','standard','menu'); ?>
shows that the position "navigation" is using the 'menu"-mod_chrome
wich is not rendering the modsuffix ...
code from modules.php:
function modChrome_menu($module, &$params, &$attribs)
{
if (!empty ($module->content)) : ?>
<div class="rt-block menu-block">
<?php echo $module->content; ?>
</div>
<?php endif;
}