In terms of access and justice, using plain language is very important. It’s needed to allow the widest variety of people with disabilities to participate in conversations about themselves. We cannot allow certain disabilities to stand in for others. Neurodivergent people (those of us whose brains are wired differently), for example, have different access needs from one another and from people whose access needs are orthopedic or purely sensory. First we must understand some more about some of the potential barriers if we are to make progress solving these access barriers.
What happens is that in-group languages, jargons, and other forms of writing that block out a lot of people from being able to read texts written by academic specialists also serve to mark the writers as belonging to special subgroups or schools of thought. These language differences are a quick way of showing the reader that the writer is a legitimate member of the system. Not only that, but an experienced reviewer can pinpoint almost exactly who the writer is, if not precisely who, by looking first at the language and then at the other writers cited and the topic of the paper combined with the language information.
When the reviewers send notes back to the original writers, the writers can tell fairly easily who reviewed their papers, if they want to, based on the commentaries, which will be written in a similar or adjacent form of jargon, and might say certain experts or methods needed to have been included or so forth, which tips you off to their subgroups. Then you can look them up on a list within the journal’s information and easily find out exactly which person they are based on their interests.
Writing in plain language makes all of this nearly impossible and marks you as an outsider. That’s part of why we do not see it happen more often in certain fields of academic activity. People are afraid they will not get published at all.