Being ambiguous to humans doesn't make it an ill-defined task. A machine which perfectly mimicked the judgements of just one human would be doing pretty well, w

Being ambiguous to humans doesn't make it an ill-defined task. A machine which perfectly mimicked the judgements of just one human would be doing pretty well, well enough that we couldn't justify saying "judging emotion is a big problem for AI" unless we said the same thing about humans. Having said that, I agree that it seems a hard problem for the foreseeable future.