Unique, meaning being the only one of its kind, is the quintessential uncomparable adjective. Because a thing either is or isn’t the only one of its kind, to say something is quite unique, somewhat unique, or more or less unique than something else is illogical.
For example, these writers use unique where interesting, curious, or unusual might make more sense:
Naima Adedapo was certainly one of the more unique and original artists on the stage on this season’s “American Idol”. [Wall Street Journal]
This new routine is very unique with a lot of circuit-style training that is done at a very quick pace. [Edmonton Journal]
For those of you who are unfamiliar with the Pulitzer process, it is one of the most unique of all the major arts prizes — for many reasons. [Los Angeles Times]
But that so many people treat unique as a comparable adjective suggests that the word has gained a secondary definition. In addition to being the only one of its kind, the word could also be defined as very remarkable or unusual.