As I read Sianne Ngai, she wants to say that emotion produces the very distance or distantiation that is at the heart of the experience of an aesthetic object qua object, via a modification (not at all Marxist) of Benjamin's concept of aura. Where for Benjamin, this sense of the object crystallizing out of a more richer intimate experience was itself only a nostalgic projection of the bourgeois conception of art (i.e. there was never any actual aura of the artwork, but rather the divorce of art from communal experience as the ruling class consolidates itself produced the retrofiction that there was, and it is now imbued with a power to ironically individualize the artwork), for Ngai, this is actually the function of emotion itself. The resulting ahistoricality of this formulation isn't entirely the most suprising thing about it, nor the complacency with which it distorts (under the aegis of modification) the already overpopular Benjamin. Rather, what's odd is it seeks to at once dissolve the process of reflection which produces the object into emotion, at the same time as it would seek to make any sort of pull away from that process also emotional, so that the solution to the objectification of the art object is also to sink it back into some even more primordial emotional structure.
But one might say that this in turn supposes that one can't present the experience of the artwork in any other form. And this is typical of an extremely regressive post-postmodern movement going on now (not conscious of the ramifications of what it is really saying, and at worst just anarchic like the high theory it seeks to replace) that would try to overcome the sort of difference-producing logics of that earlier moment by showing how more traditional logics can be based upon them instead of upon logics of presence--something akin to having your cake and eating it too. Thus Ngai cites the "post-structuralist turn away from experience" (or some interpretation of emotion as a very thin form of testimony) as all the more legitimating her return to emotion and experience (even though--and this seems forgotten--all that was actually articulated in any generally sane post-structuralist theory like Lacan or Derrida's was a distance in levels between experience and what it would not grasp). But returning to emotion and experience in order to aestheticize both, and then pass them off as difference-friendly, doesn't seem legitimated at all. What is needed is rather something like a sense that the critical presentation or exposition is indeed based upon a different logic than our experience of the text, such that both come to meet each other from different places. As it is, Ngai still supposes, like all the close readers in the post-formalist days of high theory, that our criticism unproblematically expresses our experience, and that the more detailed this gets, the more experience there would be. Instead, I would suggest that I can have an intensely emotional experience of an artwork, and yet that my present explication of it (however impassioned) does not at all immediately reflect that experience, but another one instead. Moreover, I would claim that it is only because of this that I indeed can investigate an emotional experience in any concrete way.