Had I thought about it I probably would have written "most unusual". Still, I'm not sure the pedant's case holds up on this one. Two things may differ from everything else to varying degrees; both are unique, but the one that stands apart more is arguably more so. Even among the unique support requests of 2014, Rob's email stood apart the most by a long shot.
So if something is 'more unique' than something else, it doesn't really fit the first part of the definition because they are both only one of a kind, but it fits with the second in that it is more unlike anything else than the other thing.
To be unique, all something needs is to have a collection of properties which (taken together) are possessed by no other instance within some larger population.
Even then, it's still quite possible to have multiple unique objects within a set.
This quality of "uniqueness" can then be ranked, based on how many of those unique properties (or subsets of them) are sufficient to still make the item unique.
E.g. blue sphere among blue cubes is less unique than a red sphere among blue cubes.
So yes, "more unique" is perfectly reasonable IMHO :P
Uniqueness may once have been a boolean property (I cannot say for certain one way or another), but at present it is not.
Language evolves over time, and I am no more confused by someone (mis)using "begs the question" than I am by someone using the modern definition of decimate.
[0] http://www.slate.com/articles/life/the_good_word/2005/11/the...
I think these battles are worth fighting. As does Weird Al: https://www.youtube.com/watch?v=RGWiTvYZR_w
That means they do have meaning. I'm sorry if you had trouble understanding the meaning of the words in the post. I think everyone else got it, though.