If you place a childtheme_override in your functions file you can achieve this. So taking the code in content-extensions.php make the adjustments you wish.
function childtheme_override_postmeta_authorlink() {
global $authordata;
if(is_single()){
//removed all the code here for the authordata
}
else {
$authorlink = '<span class="meta-prep meta-prep-author">' . __('By ', 'thematic') . '</span>';
$authorlink .= '<span class="author vcard">'. '<a class="url fn n" href="';
$authorlink .= get_author_posts_url($authordata->ID, $authordata->user_nicename);
$authorlink .= '" title="' . __('View all posts by ', 'thematic') . get_the_author_meta( 'display_name' ) . '">';
$authorlink .= get_the_author_meta( 'display_name' );
$authorlink .= '</a></span>';
}
return apply_filters('thematic_post_meta_authorlink', $authorlink);
}
All that will remain is the separator bar before 'published'. Can remove this with css or make another childtheme override, this time: childtheme_override_postheader_postmeta
Hope that solves it.