https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64132
--- Comment #16 from Jonathan Wakely <redi at gcc dot gnu.org> --- I suspect Debian had downstream changes to the it_IT.ISO8859-15 locale data, as was later done in upstream glibc. The original version of the test failed if it_IT.ISO8859-15 uses thousands separators. The changes in r265165 would have fixed it, by using a different locale. The test I put in comment 11 was after that change to use nl_NL, which explains why it shows no grouping. Mystery solved.
