Dave, you are being over-optimistic. The bigger community gets the more is variety of people’s opinions, that’s one reason to make such code.
The other is there are lots of young people joining in who may not have yet picked up the important rules about living amongst humans, we can help them socialise better (I am not giving any examples, but some stuff the youngsters do horrifies me, and want to think they are not being asshats, they just didn’t learn yet).
The third reason is that we come from different cultures, and it’s sometimes hard to understand why people from other culture disapprove your actions that your own culture may think are fine, so having a clear “this is how we do it HERE” rule would make it easier to explain (not to understand, but let’s save at least the nerves of people who have to solve such issues).
I have a few ideas to offer, on specific things:
After one-off larp it’s fine to discuss all character secrets between the people involved. If the larp is planned for more than one run - don’t give out the details to people who didn’t play, or you’ll spoil it for them. In campaigns discussing of people’s secrets that you found out should not happen as it ruins their plot, and we know this is a real issue sometimes, people start enthusiastically talk of this as they just don’t think this may be important to keep secret. By the way, Dave, this is a fourth point for you - people often wouldn’t just THINK something may be bad, or something is important to be done (it was mentioned before that in the past people often didn’t stay for clean up after larps because they didn’t think of this needed to be done).
The other idea, and it’s not mine but something that was discussed already, is no showing to games without prior arrangement for skipping. May I also mention it’s important to tell not just GMs but also people who are connected to your character or organising something for you regarding it (sorry, had my own hurting experience with this so I thought I’d mention).
More of many-times-mentioned ideas are: shower in campaigns, make people aware of your allergies (not necessarily campaigns only, if it’s a day game in the park and you suddenly fall down suffocating, we’d rather know beforehand that you are allergic to some plants and where in your pockets you have your spray), speak clearly when you feel uncomfortable with something (because we are not telepaths here), pay for your games on time (Jade Empire cancellation made me cry ).