>the sorts of people who will harangue mods for admonishing them to be nice will, instead, harangue the mods about how their statement wasn't actually a personal attack.
The solution there would be to make clear what constitutes a personal attack. No reason to bikeshed over it.
You can learn to push situations (using your behaviour) to obfuscate "what's actually a personal attack" greatly. Wrap your attack and words in the political language du jour, play to the biases of the moderator, there's a million ways to do it.
It seems it's pretty easy for an unbiased observer to spot that. In cases where a moderator is too biased, that's why there are multiple moderators that would all collectively make decisions about the code of conduct.
The sorts of people who choose to be moderators- especially of a project with a politically tilted code of conduct - are wont to engage in political consensus-building.
Shifting and shrinking the overton window till they all know what the acceptable views are and an orthodoxy is built.
This'll happen unless the moderators are mentally diverse. However, as the expansion of moderator teams and moderation generally is usually politically driven, this doesn't tend to be the case.
It's easy to spot! Not that there are unbiased observers. Just ones that are and aren't biased against you in particular. That doesn't mean it doesn't happen.
The solution there would be to make clear what constitutes a personal attack. No reason to bikeshed over it.