In Symfony 3.3, we stopped lowercasing the IDs of services. I propose to do the same for the container parameters in 3.4.

If you open the compiled service container, you'll find this:

public function getParameter($name)
{
    $name = strtolower($name);

    // ...
}

public function hasParameter($name)
{
    $name = strtolower($name);

    // ...
}

This means that container parameters are case insensitive in practice. I think it's better if Symfony doesn't change anything defined by the user, such as the name of the container parameters. This would also save us tens of strtolower() calls.