Some departments even have editors available to do final mark-up of manuscripts. Therefore, we need to help students be productive writers in the modes we have found useful while at the same time being clear about boundaries we require for their work. And in some disciplines, part of the ethic is co-authorship. Students need to hear explicitly, from each teacher in each course, what the boundaries are. In general, I think it is very important for faculty to define plagiarism in the context of their particular course, to do so in writing, and to do so at some length.
Genuine dishonesty is always repugnant.
We're the professionals, and students are not required to be telepathic, so the burden of clarity falls to us.