I'd also like to state the app rating has not changed in my app store, Google Play. I am based in the United States. The app store rating for me simply says "Teen" and it is based on the ERSB game ratings.
I checked mine out of curiosity and in the Swiss app store it says 13+ whereas before it was 18+ (there's only 4+, 9+, 13+, 16+ and 18+ available as rating, so PIMD being 17+ had to be 18+ in the Swiss store).
I get what you're quoting about the rating, but I do agree with others that it is really misleading and should be addressed accordingly. In my opinion it is always better to be safe than sorry, so upping the rating (or filing a request to the stores for it to be upped) at least to 16+ would be helpful. It would clearly indicate that the game isn't for children, all the while without selling it as an adults only game (though given the community, even after the channel changes, I don't think having it flagged as 18+ would be bad).
That said, back on topic: I don't think the silencing policy is wrong, on the opposite! If someone simply made the effort to read, everything is pretty straightforward in my opinion. I can understand how Campus can be confusing though given it was the main chat for everything for years, and how frustrating it can be to be silenced for an honest mistake, which is why I do agree with those who suggested a warning for the first offense — as in, you post in the wrong channel once? You get a warning. You do it again? Silenced for 24h, and the whole silencing tiers begin (I like those, they make sense!) Because if you do post again after a warning, to me it means you don't care to check and understand what was wrong. Like the warning for spanning, you know? The one that tells you that sending the same message too often is considered spamming? A warning of the same kind could be useful, though I can understand it's not easy to do — the game would be able to read the whole text, understand the content and decide if it fits the channel, which can be done I guess, but probably takes time and isn't easy (I think? Not sure but with my limited knowledge it sounds like something that can be done but not on the spot

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