Avoid username output as a class of an article tag
I think you can blame Omega for that one, in omega_alpha_preprocess_node() you'll find this:

$vars['attributes_array']['class'][] = drupal_html_class('author-' . $vars['node']-&gt;name);


I think you've got two options:


Remove that preprocess function altogether, using hook_theme_registry_alter(), and duplicate it into MYTHEME_alpha_preprocess_node(), minus the offending line.
Implement MYTHEME_alpha_preprocess_node(), search through the $vars['attributes_array']['class'] array, and remove it from there.