It seems to me that something is wrong here... earlier (https://github.com/ezsystems/ezpublish-kernel/pull/170/files#L15R526), we set `$valueLanguageCode` to the Content's main language code if the field isn't translatable. Then we compare `$valueLanguageCode` to the main language code to check if the current language's the main one.

For a non translatable field, since `$valueLanguageCode` will always be equal to the main language code, `$isLanguageMain` will always be true, isn't it ?

One consequence I see is that the `$SPIField` entry will be added for non translatable field, with the main language code's field value.