The polish manpages installed by portage are way outdated compared to the english ones. This means that many users having polish locale will not see many new features in portage documented unless they use 'LC_ALL=C man ...' Since the polish manpages seem to be unmaintained and not really useful anymore, I think it would be best to drop them.
This is fixed in 2.1.12.13 and 2.2.0_alpha188.