Sometimes players just don't get banned by sentinel. Even if you're just mildly tryharding, it can be upsetting to play against cheaters, especially if you run into the same player multiple times. While it isn't a critical feature, it's a simple thing that people have been requesting for a long time. I can assure you I am not asking for this because I think it will make them want me as a helper.
I think a clear distinction between closed and denied reports would make it easier for us to see what happened and would reduce confusion. I don't care if my report is accepted or closed as a duplicate, but I don't like getting a report denied. The moderator is telling me that I made a mistake and wrongfully reported someone with invalid evidence. Not the end of the world of course, but in that case I usually want to argue my case and possibly search for more evidence, so the distinction between closed and denied reports is important.
This is a really small feature, that also can be done by someone that is not a game developer. I see it more as a design decision than the decision if it's worth spending the time on it. At least until andyschofie left it probably would've been a matter of a few hours at most.