It's not about the _rule_ being non-self-evident, it's about enforcement being uneven. Most humans will tend to perceive lower negativity and rule-breaking behavior in viewpoints they agree with than in viewpoints they don't. A formal statement of rules allows a community to try to do away with this bias. A documented set of rules also allows a community to reflect on their own norms and allows them to make changes to their norms as the viewpoints of the community change.
I'm not sure I would state it as trying to do away with bias. Bias is inescapable. In fact, I'd go so far as to say that bias is a good thing, insofar as we want communities to be biased towards things that they prioritize and biased away from things that they don't. What a code of conduct does, in the best case, is allow a community to be explicit about its biases, allowing prospective contributors to see up-front exactly what kind of community they're joining.
Of course, there are plenty of cases communities implement codes of conduct poorly, usually in response to some crisis.
Sure
> I'd go so far as to say that bias is a good thing, insofar as we want communities to be biased towards things that they prioritize and biased away from things that they don't
I'd argue that this depends on the community. For some communities, sure, but for others not necessarily. A discussion/debate club or a book club is probably more interested in plural viewpoints. A game discussion site probably much less so, and a support group probably has a very narrow set of allowed viewpoints. But it depends.
> What a code of conduct does, in the best case, is allow a community to be explicit about its biases, allowing prospective contributors to see up-front exactly what kind of community they're joining.
Indeed. But also, communities aren't unified or static things. Different members of a community, even founding members (as we can see with TFA), will have different viewpoints on what the community means for them. A formal statement of rules lets everyone agree on an explicit, documented set of common rules that they feel accurately represent their community.
When I was younger I ran or helped run many small and medium size organizations and I've never been in one with unanimous opinions, even among very friendly founding members. Creating explicit rules has always been an improvement in pretty much any community I've been in with over 10 members. Leaving rules and procedures undocumented always resulted in games of shadow politics where there were tacit holders of power and tacit power groups and frustrated newcomers.
Do they? It seems to me that a Code of Conduct just gives these sorts of people an entirely new set of rules to litigate/bikeshed. If the Code of Conduct prohibits personal attacks, for example, 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.
>It is sad that we need to make rules like "do not be a jerk"
I don't think the problem is in the rules or lack thereof. I think the problem is there in the (lack of) enforcement. Many internet communities are allergic to anything that smacks of "censorship", and thus find themselves at a loss whenever someone comes along and willfully violates community norms. We should remember that "well kept gardens die by pacifism" [1], and no matter how detailed and elaborate the rules, someone needs to be willing to actually enforce them. A Code of Conduct (or some other formalized set of rules) can help here insofar as it allows the moderator to point to something outside their own thoughts as a justification for why they're taking action against a transgressive community member.
However, it's possible to go too far. Wikipedia is a great example of what happens when rules become too elaborate. There are many trolls on Wikipedia who are around simply because they've mastered the arcana of the various rules and procedures Wikipedia has built up in its efforts to create an "objective" standard of community behavior. Whenever they're brought up for discipline, they can point to some previous case where superficially similar behavior was excused.
[1]: https://www.greaterwrong.com/posts/tscc3e5eujrsEeFN4/well-ke...
The solution there would be to make clear what constitutes a personal attack. No reason to bikeshed over it.
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.
Now I'm certainly not claiming a CoC has unintended outcomes, but surely as often as I see them recommended (and at times even demanded), I would hope there exists decent evidence of their usefulness.
Codes of conduct deal with these self-absorbed members (they are not trolls necessarily). CoC probably help with many other things, but taking care of this low hanging fruit is already an incredible improvement.
It is sad that we need to make rules like "do not be a jerk", but sometime ago I was disillusioned from the idea that such rules are self-evident. They mean very different things to different people, so defining them ends up being useful.