Sorry to be pedantic, but your very first reference confirms what I said:

>However, sometimes the situation isn’t so cut and dried. There’s a set of adjectives (including perfect, infinite, and unique) which fall into both categories, gradable and absolute. (...)

>(...) unique has developed a weaker, less precise meaning: ‘very remarkable, special, or unusual’. The historical Oxford English Dictionary first records this sense in the 19th century, and it’s now well established. The ‘very remarkable or special’ meaning is not an absolute concept and is therefore gradable, so it’s grammatically acceptable to use modifying adverbs:

√ I saw a guy wearing some really unique eyeglasses. √ They’ve devised a highly unique way to cook and serve meals.

http://blog.oxforddictionaries.com/2012/05/an-extremely-most...

If you want to argue English usage with Shakespeare, that's your business.

"My matter hath no voice, to your own most pregnant and vouchsafed ear." -- Viola, "Twelfth Night"

Pedantic but the misuse of "unique" is semantics not grammar.

I thought we'd all learned to stop worrying and love descriptivism?

Pedantry aside, I'd like to suggest that common sense and should always trump grammatical "rules". If we might assume the layperson's definition, "one of a kind" (ie, one instance in a set), and acknowledge that one such kind may represent a radically larger set than another, how might we use English to describe the difference?

The letter "R" is unique in the English alphabet. The particular grain of sand in the palm of my hand is unique to the world's beaches.

Are "R" and this grain of sand equally unique? Might there be a way to compare them?

I don't want to debate the point, rather to pose the question and see what any responses might illuminate.

Have a nice day. :)