That is pedantry. I understand your point, but when people say something is "very" unique, they mean it's not common, or is unusual in some way. "Slightly unique" makes little sense, but "somewhat unique", while somewhat awkward, can mean "unique in some aspects, but not others".
And if you want to be really pedantic, then you have to admit that most anything can be considered unique at fine enough levels of detail. But there is no point to calling something "unique" then; it loses meaning if everything is in fact unique. Uniqueness really is more of a spectrum, when applied to the real world.
I'm trying to decide if I should be insulted or not. Is the comment stating that the stereotype is that Mormon women are frequently pregnant? I'm not sure what point you're trying to make.
edit: Thanks for the clarifying comments, I didn't catch that the comment was referring to the grammer.
To quote an English comedy show: "One can not have gradations of uniqueness. A thing either is, or is not, unique". I believe he is commenting on your use of the term "very unique".
vixen99 is saying you can't be a little unique, or very unique, but simply unique. Just as nobody is "slightly pregnant". No need to be insulted, though you may disagree with the assertion.
