Academic writing follows the guidelines of formal English: the way writing is taught in grade school. Standard grammar and punctuation rules reign, and paragraphs use the traditional format of topic sentence, support and concluding sentence. Writer's seldom use discretion, and grammar book lessons are reflected in the writing. Standard state assessments and common college admission tests, such as the ACT and SAT, use the formal language in academic writing in their questions. When in doubt, the academic writer should find a rule to support his decision to use or omit a comma and other mechanical inclusions.
Commonplace conversation creates foggy areas for academic writers. Some think that if something in spoken language is acceptable, then it should likewise be okay in writing. This conclusion is not the accepted norm for academic writing. For example, people often say "Jim and I" regardless of the case. "Jim and I" is only correct in the nominative case (subject), and "Jim and me" is correct in the objective case (object). The "and I" has been so misused that the rule often gets overlooked, but in academic writing it must be applied.
Additionally, when people speak, one might swear that the words "might of been" are used, but there is no such expression in formal English. The correct expression is "might have been."
Business writing is much more lenient with the English language rules and allows for a great deal of writer's discretion. When a grammar rule states that some deviance is acceptable, and it is shorter or simpler, the business writer often will use the deviant option. Business writing is about shortcuts and concise writing- saying what you need to say in as brief and simple a manner as possible. Punctuation may be considered clutter in business writing, and it is used sparingly.
Many of the shortcuts business writing takes are acceptable, and some are just unbelievable. One legitimate example is the use of commas in a list or series. Formal language tells the writer to use a comma before the "and" preceding the final item, but it is acceptable to omit that comma. Business writing will almost always omit that final comma.
A more daring example is in the case of General Motors some years ago. The company elected to change the spelling of the word "employee" to "employe." The reasoning was cost savings: less time to type and less printing. Not surprisingly, it was not ever really accepted and the proposed policy began to cost more than the anticipated savings. Business writing must be cautious to remain in the acceptable category.