As a copy editor for a professional journal, how far should I go in adjusting the wording of an article?
I think a reasonable rule to follow when editing an accepted manuscript prior to publication is to make the minimum changes required to conform with proper grammar as well as whatever style guide your publication uses. (The latter might include, for instance, citation formats as well as the use of British versus American English for spelling.)

If there is ambiguity in editing possibilities, I would propose the change to the authors, but also, if possible, flag it as an "author query" to ensure that the change is viewed and a consensus reached.