I doubt clothing could be a full human language. A human language is a remarkable thing. Our language ability is one of our chief adaptations as a species, with it I can conjour the precise and bizarre notion of a purple bus-driver giraffe with those few mere phenoms.
I would imagine we must have some systems for interpreting information about other humans from their accoutrements, but I would also imagine that they surely cannot be as highly developed as our language, as the technology to have different 'styles' or even clothes at all is relatively recent. Also as a bit of anecdotal evidence I present that, any healthy human growing up around at least one other human will develop a spoken language, or adopt the language of their peers. In contract there are examples of people growing up in societies with clothes and style who do not develop any particular style sense.
So I posit that this style language is relatively limited and only certain pre-arranged messages determined by society can be communicated by it. Also it seems extremely prone to misinterpretation . Both parties must be aware of, and agree on, the pre-arranged signals for it to work.
Which is why I personally dont even consider it. With such a limited and error prone language how could I accurately communicate anything meaningful, or personal, or that I particularly value, about myself. Also why would I would I want to blast out this signal to all and sundry?