[raiph]

> I expect that if you try out the Python version on your system you'll also get the "right" answer.

I don't think so. In my tests standard python (2.7 and 3.5) ignores grapheme clusters.

[masklinn]

Python ignores grapheme cluster, that point was about my original test case using grapheme clusters I later found out had precomposed equivalent, so a transfer chain performing NFC would leave the test case with no combining characters (or multi-codepoint grapheme clusters) left in it.

[raiph]

Gotchya.