The general grammatical rule as per the U.S.'s MLA (Modern Language Association) is that a comma and a coordinating conjunction ("fanboys" - for, and, nor, but, or, yet, so) connect two sentences together. The coordinating conjunction does just that, coordinates the meaning of the two either in comparison or in contrast to one another. For this reason, many English instructors "follow the rules" to teach the best possible way to convey meaning using symbols and usage familiar to the majority of readers. However, American modern and post-modern writers have been differentiating themselves along the historical trail by playing with language in all of its forms and structures. As per other examples in American English, creativity with the language often results in new standards forming that displace the old. Some see this as a corrosion of language, others as creative expression by a diverse linguistic culture