I guess it's the same thing as pocket squares themselves, which less knowledgeable folks consider a "formal" accesory, when in reality the most formal city look is no PS at all...
Orgetorix, it wasn't my post, I'm actually with you on this one!
I meant that a lot of people think of a PS as a "formal" accesory (which I think it isn't, at least not in an inherent way), and what Roger Everett said about bow ties seems to be in the same line of thinking.
I don't believe it's a so called "rule", but I never wear ties of any kind with buttoned collars. I personally just don't like the way it looks. But I see so many people doing it that they must see something in it that I do not.
I like BD collars with more casual options, like a tweed jacket with a challis tie, or with a bow tie (though I can't pull of a bow myself, but I like it when others do). Not with a formal tie + suit, though that seems rather common in America, so it may be OK over there.
Es broma! No guardias de seguridad dress like that here either. But navy blazer + grey trousers is seen as the "security guard look" in this forum, right?