https://github.com/symfony/symfony/blob/v3.0.6/src/Symfony/Bridge/Monolog/Handler/ConsoleHandler.php#L175

That seems wrong. An Output configured as VERBOSITY_QUIET (which is triggered e.g. by running a console command with -q) doesn't mean that nothing should be printed, just very little. E.g. unhandled console command exceptions get reported under VERBOSITY_QUIET. The ConsoleHandler is apparently hard-coded to never output anything to such an output, even though its behaviour is otherwise supposed to be configurable via the verbosityLevelMap parameter.