Where to draw the line when giving feedback?
A first point is to ask what is the purpose of the activity to be graded? Is it to test student's knowledge, or is it to provide a learning activity? If it is the former, then feedback before grading seems counter-productive. If it is the latter then the feedback is necessary to provide the sought effect.

I am experiencing this problem with student theses. In the system where I work, the thesis is considered an individual work and grading it should take into consideration qualities such as originality and independence and yet the student has a supervisor who should provide input. The task is caught in the middle between examination of a task and a learning experience; and each supervisor has their own take on where the limits are. So why is this such a mess?

The key lies in failing to define what is a learning experience and what is a test of knowledge or understanding. Hence it is necessary to try to define these points so that the division becomes clear to all concerned. The key lies in deciding the balance between the two. Feedback provided after grading is, in my opinion a lost cause since students have moved on to other activities and very few probably run through the comments. Better is then to, for example, build in the feedback into the grading. This can be done by setting a preliminary grade and stating that successfully working through (not just any work-through) comments to improve the task will provide additional points or step up to a higher grade. This may be incentive enough for most to do the extra work and for those who do not want to, well that will be their decision.

So a key ingredient will be to build in the feedback--improvement into the grading of the task. exactly how to do this will of course vary depending on the task at hand.