TYPO3.Flow

If the TranslateViewHelper will passed "arguments" and this is now an array of a single number [array(0 => 123)], for example to tell that the password is too short, the Translator (\TYPO3\Flow\I18n\Translator) try's to find the plural form of this number (take a look in \TYPO3\Flow\I18n\Translator->translateById() which is called \TYPO3\Flow\I18n\Translator->getPluralForm()).
Normally this fails and the ViewHelper returns the passed "id" or "value".

The following line returns "Password must have x characters.", even if "myMessageId" is set correctly.

{f:translate(id:'myMessageId', arguments:{0:123}, value:'Password must have x characters.')}

If "myMessageId" use the placeholder {1} and

{f:translate(id:'myMessageId', arguments:{0:1, 1:123}, value:'Password must have x characters.')}