An insightful essay, as always, but I think Aaron both overstates the extent to which persona is manufactured on Twitter and understates the extent to which persona is manufactured in interpersonal exchanges.
That is, we're always giving a performance of ourselves to others, but to the extent that we are what we do, we are the personas we choose to present.
Twitter as a medium obviously has some specific characteristics that both enable and constrain what kind of communication can take place across it; but again this is true of all media - including face-to-face conversation.
I think the original question is unanswerable, since Twitter is a different thing for different people, while the author focuses to just several use cases. I personally use Twitter mostly as a real-time search engine and it proven to be useful in this regard.
That is, we're always giving a performance of ourselves to others, but to the extent that we are what we do, we are the personas we choose to present.
Twitter as a medium obviously has some specific characteristics that both enable and constrain what kind of communication can take place across it; but again this is true of all media - including face-to-face conversation.