I usually try to avoid things that are "political" in nature, but I will say something here because I think people being mean to problemsetters/coordinators is very very bad, and this problem is an especially bad instance of it!

I agree that the preparation of the problem was a bit sloppy due to not having an exponential bruteforce for the final version of the problem, but here's a few reasons why this does not warrant verbal punishment:

• In general, there's probably some small probability that any problemsetting team unintentionally produces an incorrect problem. Different teams have different probabilities, and them actually producing an incorrect problem is probably correlated with the probability, but it's unfair to place immense blame on those who do. I think the correct attitude is to consider it an unlucky accident when it happens. As much as we like to pretend that we can prove things infallibly, this is simply not the case because we're human.
• Preparing a problem lacking an exponential bruteforce arguably shouldn't be done when creating one is possible, but it's very understandable why this could be skipped — writing such things are tedious, especially if you have to do it for every single problem. And I get the sense that competitive programmers really dislike tedious things. And in this case it was actually more nuanced than that, because there was an exponential bruteforce to the original correct version of the problem, and it makes sense that one could be too lazy/forget to change it. The incentive to not write a bruteforce is made even stronger by the fact that 99% of the time it was probably unnecessary.
• It was unintentional. I believe that problemsetters/coordinators do their job out of passion, and we should only be thankful to them for giving us fun things to do. I don't like the idea that there is fear of getting downvoted/hated due to something you didn't intend. In fact, in this case, it doesn't even make sense to downvote the announcement because they didn't contribute to the mistake.

Additionally, saying something mean to them because you would've had a good performance is quite silly because rating changes are pretty much zero-sum, so unrating any round would probably not affect the sum of rating change-induced happiness (I know that happiness might not be directly proportional to the size of the change, but whatever). In fact, this would've been my best perf in a while :(

Another point that has been brought up is "how did some large % of div1 participants proof-by-AC the problem? they are all sheeple!" I, unfortunately, am one of the sheeple. At least for me, I did not intentionally proof-by-AC. The mistake in my fake-proof was that I thought the following statement is true: "f != g => the first non-consecutive swap reduces the number of inversions by > 1". Since we're trained so much to use the strategy of "guess a necessary/sufficient condition, and then prove that it's sufficient/necessary", it's easy to be sloppy with the proof part because we also want to AC fast. In fact, it seems to me that most of the sheeple-accusers didn't even rule out the fake-solution by finding a hole in the proof, but by directly finding a countertest.

In conclusion, to the people preparing problems, please keep doing it so that I can one day become the grandmaster!