I believe there is actually a plugin or module on the site that is trying to render EasySocial's language file and it is doing it wrong. However, there are just too many plugins on your site to try to disable them one by one.
To fix this, I have copied the codes below,
[gist]
COM_EASYSOCIAL_PRIVACY_OPTION_PUBLIC="Chiunque"
COM_EASYSOCIAL_PRIVACY_OPTION_MEMBER="Utenti Registrati"
COM_EASYSOCIAL_PRIVACY_OPTION_FRIEND="I miei Amici"
COM_EASYSOCIAL_PRIVACY_OPTION_FRIENDS_OF_FRIEND="Solo gli amici dei miei amici"
COM_EASYSOCIAL_PRIVACY_OPTION_CUSTOM="Personalizzato"
COM_EASYSOCIAL_PRIVACY_OPTION_ONLY_ME="Solo con Me"
[/gist]
Into /language/overrides/it-IT.override.ini and the translation is appearing correctly now.