(Note: I do not edit the references)
My editing goal is to ensure that the edited text faithfully conveys the author's intended meaning. However, sometimes, authors write statements that are very ambiguous.
For example: "There are thousands of patients with diagnosed multiple sclerosis every year and require TNFalpha treatment [ref1]."
This could be interpreted as "Thousands of patients are diagnosed with multiple sclerosis every year, many of whom eventually require TNFalpha treatment [ref1]" OR "Every year, thousands of patients who have been diagnosed with multiple sclerosis require treatment with TNFalpha [ref1]."
This kind of ambiguity impedes the smooth flow of concepts and can obscure the key messages of the manuscript. To eliminate it while ensuring high-fidelity editing, I use what I term Reference-based Editing. Thus, I will check the Abstract (or, if readily available, the online paper) of the cited text (in this case, ref1) to determine what the author means.
This approach also allows me to occasionally pick up referencing mistakes (such as citing the wrong paper) and to rewrite texts that resemble passages in the published paper too closely. The latter is a common inadvertent error made by authors who have difficulties writing in English but it can lead to rejection by the journal on the basis of plagiarism software, which many journals use routinely.
Reference-based Editing means that I can also offer versions of the original text that explain the point more precisely. For example, "Effort to improve antibiotic use has started a few years ago in Sri Lanka[ref9]". To improve this, I will check reference 9 and suggest to the author that the following reformulated sentence may be more suitable: "To improve antibiotic use in Sri Lanka, the government launched their first antibiotic stewardship program in 2011 [ref]."
Because I sometimes rely heavily on Reference-based Editing, I strongly encourage authors to supply the relevant bibliography.
Occasionally, even with Reference-based Editing, it is not possible to discern what the author means. In such cases, I will explain why the sentence is confusing and if possible, rewrite the text according to an educated guess: this rewritten text will be marked by an editor comment. I can sometimes also provide one or more alternatives in the comments: this allows the author to choose which version best captures their intended meaning.