sys-apps/texinfo-6.7 is picky about non-ASCII characters in texinfo files, if the file doesn't declare @documentencoding. This is seen at least with files in the ISO-8859-1 encoding. Not sure if it actually occurs with files that are UTF-8, however, the texinfo manual says that @documentencoding should be declared for anything that isn't ASCII. Typical error message: utf8 "\xF8" does not map to Unicode at /usr/share/texinfo/Texinfo/ParserNonXS.pm line 1796, <FH> line 1448. Malformed UTF-8 character: \xf8\x72\x6c\x79\x6b (unexpected non-continuation byte 0x72, immediately after start byte 0xf8; need 5 bytes, got 1) in pattern match (m//) at /usr/share/texinfo/Texinfo/ParserNonXS.pm line 3364. Malformed UTF-8 character (fatal) at /usr/share/texinfo/Texinfo/ParserNonXS.pm line 3364. Example of bug fix: https://gitweb.gentoo.org/repo/gentoo.git/tree/app-emacs/mmm-mode/files/mmm-mode-0.5.7-texinfo-encoding.patch?id=2d5224988c9036b05242b207dfe8f1c9221c7d28
Seems like nothing left to do here.