If you are quoting someone or something as an authority in support of what you are discussing, identify the source in the text. If you are using a quotation because it is a succinct way of stating something, you need not identify the source in the text. Both types of quotations, however, must be documented in the endnotes. For more information on nonsexist writing, see Casey Miller and Kate Swift, The Handbook of Nonsexist Writing , 2d ed. Often, due to fluidity of language, it is impossible to stay consistent within the same article.
Interchangeable use is permissible.
We prefer that you stay true to historical context. When quotations from subjects are used, it is usually desirable to clean up the grammar to some extent. A journal article is not a literary endeavor, in which dialogue is important to meaning, nuance, and tone. The point here is to relay information. In this format, maintaining ungrammatical English could convey a tone of condescension, a certain smugness.