I tend to offer a lot of feedback within a written document assignment, because I instruct writing and therefore the conceptual process is visible in the text on several levels, both in content and ability to articulate that content.
One of the biggest frustrations I have as an OL teacher is that it is obvious that many students do not read feedback carefully, if they read it at all. For example, the student who makes the same errors repeatedly, even though I urge them to read my feedback on the commentary section of the grading rubric.
In all fairness I do witness this in the FTF courses I teach also. The students who do best are usually those who meet in person in my office to go over an assignment. I try to replicate this FTF input in an email dialogue with students if they contact me about a problem they are having.