As explained in eZ/Publish/Core/Persistence/Legacy/EzcDbHandler.php:

PDOMySQL ignores the "charset" param until PHP 5.3.6.
We then need to force it to use an init command.
@link http://php.net/manual/en/ref.pdo-mysql.connection.php

public static function create( $dbParams )
...
$databaseType = $dbParams['type'];
if ( $databaseType === 'mysql' && $dbParams['charset'] === 'utf8' )
{
	$dbParams['driver-opts'] += array(
		\PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8',
	);
}

The problem is the SET NAMES utf8 will only be execute if the database settings in ezpublish.yml has the charset: uf8 line, what it doesn't by default.

It's important that the documentation is clear that, if PHP versions prior than PHP 5.3.6 are used, the charset: uf8 line must be used as well in the database settings to avoid charset problems.