When I've flagged a post, the corresponding pop-up just seems to disappear and I'm not sure if the flag was successful or not. It's very confusing. I see this request, which seems to have high reviews, but little feedback. I don't understand why it isn't requested more frequently; the current system is very counter-intuitive and leaves me wondering.
Any form of display that my flag went through successfully would be extremely useful. The link I provided is actually a very good suggestion.