For the Sake of Consistency
Some “rules” of writing are up for debate. Indeed, certain elements are actually not hard and fast rules; rather, they are open for interpretation and choice. For example, the hotly debated “serial comma” (i.e., the comma following the “and” in a series of items) may cause grammarians considerable consternation, but in the end, the writer can choose whether to include the serial comma or not. Another example is the block or indented formatting for paragraphs. Should each new paragraph be indented, say five spaces? Or should each paragraph appear flush with the left margin and a line space included between the two paragraphs? In essence, that is up to the writer. Either is acceptable.
However, one thing remains unacceptable, i.e., inconsistency. Once you make a choice on a writing style, you should consistently use that style. If you use the serial comma once, you should use it in all appropriate situations. If you use the block format at the beginning of your document, you should use it throughout.
Another area where consistency is sometimes lacking is the choice of adhering to British writing styles and spelling conventions versus American writing styles and spelling conventions. Either is acceptable, but you must choose one and stick with it throughout your document. The use of acronyms is another example. If you choose to use an acronym, you should use in for every reference of that term throughout the document after you define the acronym in question.
Overall, consistency is quite important in the written text. Be sure that you follow the same stylistic and formatting choices that you make at the beginning of the text, including the ways in which you format headings and subheadings. This will ease the flow of your text and minimize confusion for your reader.