In coreutils 7.5, the sort -h option doesn't work in a UTF-8 locale, because the coreutils-i18n patch includes a new keycompare (keycompare_mb), which doesn't call human_numcompare.

The culprit is lines 2245-2256 of the patch file, reading:

+ else if (key->numeric | key->general_numeric)
+ {
+ char savea = *lima, saveb = *limb;
+
+ *lima = *limb = '\0';
+ if (force_general_numcompare)
+ diff = general_numcompare (texta, textb);
+ else
+ diff = ((key->numeric ? numcompare : general_numcompare)
+ (texta, textb));
+ *lima = savea, *limb = saveb;
+ }

which should read like the old keycompare (now keycompare_uni):

+ else if (key->numeric | key->general_numeric | key->human_numeric)
+ {
+ char savea = *lima, saveb = *limb;
+
+ *lima = *limb = '\0';
+ diff = (key->numeric ? numcompare (texta, textb)
+ : key->general_numeric ? general_numcompare (texta, textb)
+ : human_numcompare (texta, textb, key));
+ *lima = savea, *limb = saveb;
+ }

or similar.