Some texts can be read quickly by the instructor to determine whether the student in on track. Some writing does not have to be read by the instructor at all. Writing is a skill only . There are certainly skill features connected with writing, but writing always takes place in a context. One can't learn to write well only by learning discrete skills separated from a context of inquiry.
Academic writing encompasses a variety of genres and styles.
There is NO one form which is common to all disciplines. Many disciplines, including Literary studies and Rhetoric and composition studies, allow the use of contractions in certain journals and published books. We often use these words to create a rhetorical effect at the beginning of a sentence. If when we use them, however, we create a rhetorically ineffective sentence fragment, then we have used them incorrectly. Comma rules are easy to learn .