Why not? Everybody's doing it these days.
I think it goes without saying that there's some pretty severe author-reader interaction going on in fanfiction. First, we have the work's original author: the mangaka, the movie screenwriter, the author of the book. Then we have the author-reader: the reader who consumed the original work and decided to write a story based on that work. Lastly, we have the reader: the person who has (probably) read the original work and is now enjoying the fanfiction based on that work.
There are many different reader-response theories out there - and it's been quite some time since I've studied any of them. Purdue's OWL website has a decent beginner's explanation (it's actually simpler to understand than the Wikipedia entry). Check it out HERE.
I think it's important to jump immediately to the "death of the author" concept first because it honestly will simplify things greatly. That means we remove the original author from the mix right off the bat. In other words, it no longer matters that Marvel and the MCU don't envision Steve Rogers and Bucky Barnes as being in love. The fans do, and so does our author-reader. Unless we're concerned about the legalities of playing with someone else's intellectual property, we're no longer really concerned about the original author's intentions.
(For the sake of today's argument, anyway.)
If a text does not truly begin to exist until it's been read, then that means a text can have a variety of interpretations. For example, one author-reader envisions Steve being in love with Peggy; another author-reader envisions Steve being in love with Bucky. Both of these texts are "right." You might point out that Steve is canonically in love with Peggy but not with Bucky. But consider this: a reader comes along who is not familiar with the original author's work; she only consumes the author-reader's work. For that reader, Steve may therefore be canonically in love with Bucky, and Peggy may have never existed.
Whew. Still with me?
Consider, too, what both author-readers and readers bring to the table. Many fanfiction writers include so-called disclaimers with their stories, saying that writing the story helped them deal with real life problems, such as depression, anxiety, a recent break-up, and so on. "This fic is my way of coping with feeling like I had been led on the entire time," explains one writer. In this story, the author-reader writes about a character who experiences a bad break-up, presumably to help them cope with their own real life situation. Had they not gone through that particular situation, the story may not have turned out as it did - or may not have been written at all.
Readers, too, can approach a story while under the influence of a variety of factors: stress, sleepiness, depression, and so on. Stories are even given labels like "hurt/comfort" to let readers know what kind of content to expect - in this instance, the reader can expect to read about characters who will undergo some sort of stressful situation but will ultimately have their stories end happily. This warning, in turn, helps a reader who may be experiencing depression look for and find a story that will help them simultaneously enjoy the Schadenfreude of reading about others who are sad as well as the catharsis of seeing those characters end up living happily ever after. The above mentioned story, for example, includes the tags "Fluff and Angst," "initially unrequited love," and "DEFINITE EVENTUAL REQUITED LOVE." They want to leave the reader in little doubt what to expect on an emotional level when reading this story.
All right, then? Moving on.
I would imagine anyone who actively engages in fanfiction, whether as a reader, a writer, or both, has likely come across a particular new phenomenon: character x reader fanfiction. In this type of fanfiction, the main character is "you," the reader. The story is therefore written in second person. The secondary character is generally one of the main characters from the original author's work. So, in a "Bucky Barnes x you" fanfiction, you are the main character, and Bucky Barnes is the secondary character and is probably engaging in a romantic encounter with you.
The word "you" can be confusing in English. I say "you" in this blog to speak directly to the people reading it. I can't speak to any of you in person (well I could, and that would be delightful, but generally I can't), so I do so via "you." "You" is therefore anyone reading this blog.
In "character x you" stories, "you" becomes both the reader and the main character. Thus the reader is engaging with the text in a more active sense than she normally would be, even more than any other type of fanfiction. Of course, the reader can't actually choose what she's doing; she's reading about what is being done too her - you can see how this type of story can tend toward the more erotic side of things.
Thus is the reader made simultaneously powerful and passive; she both gains and loses agency. Of course, if the story makes her uncomfortable, she has the power to simply navigate away from it. But that story - her version of that story - cannot exist without her. Without her, Bucky Barnes is romancing no one at all. (Poor Bucky - always gets the short end of the stick, doesn't he.)
Considering the sudden prevalence of this unique type of fanfiction, I think it demands further study. I'd love to interview people who read and enjoy such stories. I'd love to interview the writers, too. What would drive an author-reader to produce this type of story? There would have to be an intense desire to please or garner some other sort of response from the reader; this, to me, is an entirely unique motivation for an author-reader and makes the original author seem even more removed than ever.
So, gentle readers, any thoughts here? Have you yet to engage with any of these unusual type of fan stories? What do you think of them? Should reader-response theorists not be chomping at the bit to dive into these bizarre little gems? Let me know what you think!