Cuales versiones del español son más difíciles de comprender si uno no es de ese país?

Ya que soy Panameño, para mí sería muy difícil comprender el español Argentino y el Castellaño.

Does academic writing that is not accessible (understandable) to the general audience, useless?

Academic writing is often times pompous. By this I mean that authors of various papers and publications use large words, not necessarily to make their point clearer, but to legitimize their piece and elevate it to an academic standard. This, often times, backfires as it is not accessible to a wider population of readers. I think academic writing has a responsibility of not only possessing great content, but also making that same content accessible to a larger market.

What are the dangers behind an Ethnic Studies academic department?

Ethnic Studies in and of itself is a very broad term. If one were to be more specific, for example, Asian and Pacific Islander American Studies, it would still be a very broad term because, in reality, an ethnicity cannot be solidly defined. That being said, the pursuit of Ethnic Studies is a necessary one as it reveals the various flaws the modern education system has.