In the rules for the Pit, it is stated that it is where you can complain about other posters. It then goes on to state what isn’t allowed in those complaints; hate speech, wishing harm on another poster, trolling, doxxing, and harassment. It doesn’t contain a restriction about accusing someone of trolling. Most rules about conduct between posters don’t apply there.
Although the standards of discourse are looser than in the other forums, the Pit is NOT a free-for-all - you don’t have to be nice, but you do have to be reasonably civil.
But the best way to know that there is an exception to the rule there is because people are allowed to do it. Honestly there doesn’t need to be any more than that. It’s really obvious.