In this article, Luu examines reaction gifs as formed in the context of second literacy (the phrase ’second literacy’ comes from Marshall McLuhan’s book, Understanding Media and it’s based on the idea that language works so radically different in writing and in digital writing that they are separate literacies). I would call attention to the part that might be the most interesting to the research of fandom communities:
„Thus, reaction gifs identify gestures in body language which are already prevalent in general pop culture. These are further defined and stylized through frequent usage by an online community. It is because these emotional responses are often well-worn tropes from film and narrative, based in a culture’s knowledge of nonlinguistic cues, that they can be more easily shared and understood. Simple emoticons can be used straightforwardly in text to signal an emotional cue. A reaction gif seems to be used more creatively as a meta-commentary than purely authentically for conveying emotion (and) it could be argued that it was not until the popularity of reaction gifs that speakers began to develop a robust shared lexicon of online gestures and that this began to move into speech itself.”
The part I would emphasize is how Luu draws a difference between trying to convey the speaker’s body language (which is also part of any written language) and invoking pop culture trope gestures. The repetetive using of these gifs extends our vocabulary beyond words and idioms: now we have reaction gifs (and memes and emoticons), too. Of course, even people outside of fandom use this vocabulary, too. But to understand why there is an added layer to communicate Captain Picard facepalming, we need to look at fannish practices and fannish usage of language (and as any linguist would tell you that, that is an infinitely fascinating area).
Luu, Chi. 2015. “All the feels: the morphology of reaction gifs” JSTOR Daily https://daily.jstor.org/the-morphology-of-reaction-gifs/