Yes they are unique characters. I went to some pains to ensure I used the word 'key' as in physical switch on a keyboard. However I did not go far enough in ensuring I was referring to the font package as opposed to the font, please accept my apologies.

It is the font package, look at iverg's comment on the github issue https://github.com/googlei18n/noto-fonts/issues/736

here are screenshots with local font installed http://i.imgur.com/ycRs3A0.png

and without local font http://i.imgur.com/TUKsIY4.png

EDIT: it goes deeper: https://news.ycombinator.com/item?id=12656642