Remove Howdy

try to add this to functions.php of your theme:

add_action( 'wp_before_admin_bar_render', 'personalize_adminbar_appearance' );

function personalize_adminbar_appearance() {
	global $wp_admin_bar;
	$current_user = wp_get_current_user();
	$user_id      = get_current_user_id();
	$avatar = get_avatar( $user_id, 16 );
	$wp_admin_bar->add_menu( array(
		'id'        => 'my-account',
		'title'     => 'Wwelcome ' . $current_user->display_name . $avatar )
	);
}

As a different option, I use this in 3.5.2:

add_filter( 'gettext', 'change_howdy_text', 10, 2 );
function change_howdy_text( $translation, $original ) {
    if( 'Howdy, %1$s' == $original )
        $translation = 'Logged in as %1$s';
    return $translation;
}

Works fine for me; might be something else in your functions.php file.

function replace_howdy( $wp_admin_bar ) {
    $my_account=$wp_admin_bar->get_node('my-account');
    $newtitle = str_replace( 'Howdy,', 'Welcome', $my_account->title );
    $wp_admin_bar->add_node( array(
        'id' => 'my-account',
        'title' => $newtitle,
    ) );
}
add_filter( 'admin_bar_menu', 'replace_howdy',25 );