Is it unethical to not give feedback on final exams or assignments? In this question a person working as a TA was asking if and how he should try to persuade a lecturer to change her practice, in which she gave grades for final assignments but not detailed feedback. Many of the comments there expressed sentiments such as this being an "injustice", "reprehensible", "unethical behavior", "moral duty", "refusing to do her job", and "worth firing for". 

Now, I must admit that I was somewhat surprised by these reactions. My experience throughout my academic career is that this is usually infeasible for a number of reasons, e.g.:


The institution may collect and impound all final exams after a day or two. 
Final exams may be given on an institutional computerized platform, for which no per-item feedback is available to either students or instructors. 
Students don't usually have time to come back to campus after finals are given. 
I don't think I ever received final exams back throughout my undergraduate days. 
I didn't get comprehensive exams back or feedback from the end of my Master's. 


I think there's even an argument to be made vis-a-vis the formative vs. summative assessment distinction that final grades and feedback should not be overlapped, and that doing so is actually not helpful to students. (E.g.: "Summative assessments happen too far down the learning path to provide information at the classroom level and to make instructional adjustments and interventions during the learning process." Link.) In that sense, one could conceivably give copious feedback early in the semester with no grade, and then a course grade only from a final assignment at the end, after one is done with all feedback cycles. 

Personally, I try to find ways to give final feedback to students if they are in critical need of it (usually by email), but I actually have to wrestle against my institution's procedures to make that happen. (I'm at a large urban community college in the U.S.) But my intuition was that it's at least a judgement call, and most common to not expect to see feedback from a final. 

So: Is there consensus that not giving feedback on final exams/assignments is obviously unethical? (Side question: Are there any statistics on how common it is one way or the other?)
I think there's a distinction between automatically providing feed, and having access to feedback.

Like many people, I give little to no feedback on final exams for basically the reasons you describe: students don't have a chance to see it until the next semester, and very few of them bother to.

On the other hand, when a student does come see the exam, I'll spend a few minutes answering questions and explaining the grade. I think this is necessary, because students should have the option of asking for  mistakes or inconsistencies to be corrected, and they have no way of doing so unless they know why they were marked the way they were.

Many of the accusations of unethical behavior in the discussion on the question you linked to seem to be driven by concerns about the latter issue: the suspicion that students wouldn't have access to any feedback if they requested it, and that this was an intentional attempt to prevent students from appealing their grade.