> When used in this way, the bracketed information should be an addition, not a substitution. For example, if the original quotation is “She never called back,” do not change it to “[Lucy] never called back.” Instead write: “She [Lucy] never called back.” (Note: Many newspapers ignore this rule. In professional and academic writing, it is better to follow it.)
Says who?
About the only real "rule" I can think of in English is that you use "an" iff the following word starts with a vowel sound. But even some people (idiots) break that rule for the weirdly specific case of 'historic'.