There's a certain kind of genius to those of us that can turn every piece of wisdom into a phrase that's worth quoting. Nietzsche, probably, being the most prominent of them all. A sentence becomes a quote, in my view, in one of two ways. In the first scenario, a quote is no more than an aesthetic structure, into which we instil meaning through the context under which the sentence is being repeatedly put to use. The second scenario would be that an idea is commonly known but hard to put to words, up until a succinct description of it is provided as a quotable phrase.
What's notably missing from both of the scenarios described above is the creation of new knowledge. And indeed, to contribute a quotable phrase is to contribute no new knowledge to the world. This is clearly a differentiation from everyday speech, in which sentences always transfer knowledge (apart from the extreme cases of the content-free language, used in Academia and the corporate world).
A certain philosopher of our times, whose books I've never read, might argue that knowledge doesn't really exist until it is transferred as discourse. It is my humble opinion, that the complete identification of knowledge with it's presentable form is misleading, and that the thought that knowledge is created only from discourse is the same as if we were to think that the fable is that which brings about the moral.