redirect more users to feedback page

app/models/submission.rb

@@ -101,7 +101,10 @@ class Submission < ApplicationRecord
   end
 
   def redirect_to_feedback?
-    ((user_id + exercise.created_at.to_i) % 10 == 1) && exercise.needs_more_feedback?
+    # Redirect 10% of users to the exercise feedback page. Ensure, that always the
+    # same users get redirected per exercise and different users for different exercises.
+    # If desired, the number of feedbacks can be limited with exercise.needs_more_feedback?
+    (user_id + exercise.created_at.to_i) % 10 == 1
   end
 
   def own_unsolved_rfc