In Nomine: R&D has a fairly minimal conduct policy. Generally, we rely on individuals to be mature because they want to keep a good reputation with others, rather than because they fear any staffly punishment. This is mostly out of a concern for abuse or the suggestion of abuse by staff, but arguably it's also just more effective. The details of this policy are explained here.
Say Whatever[]
You can say pretty much whatever you want. You can swear at the headwiz without worry. If you want, you can complain about another's roleplay or character in the strongest terms. (Tact is nonetheless a good idea for reasons other than avoiding punishment, including not being a jerk.) The environment we want to create is one of free-speech and the open expression of ideas. We rely on good ideas to beat out the bad ideas over time. This can't happen if people are afraid of getting in trouble with admin because so-and-so knows so-and-so. With the right to say anything comes the responsibility to be mature and suck it up if what someone says makes you mad: either make a reply or forget about it.
There are, however, certain exceptions to the anything goes principle:
Offensive Language[]
This might sound like a total backtrack, but it's really just a qualification for extreme cases. Try to keep talk on public channels at least somewhat palatable to the average person. It doesn't need to be sanitized, by any means, but don't get too vulgar. This rule will be invoked very rarely, and people will always be privately and publicly notified by a staffer. Honestly, the motivation for this rule was a thought experiment in which someone just tried to gross everyone out, and staff was technically without any means by which to tell them to cut it out. It's here for the possible situation in which some jerk deliberately tries to disturb people, and is not meant to police ordinary conversation. Please don't worry about it.
No Unauthorized Release of Personal Information[]
It is not permitted to spread another roleplayer's personal RL information to others without that individual's consent. Don't post phone numbers or addresses. Don't name names. Don't Google-stalk people and post links to photos of them after their recent facial surgery. Don't post people's LJs that you've discovered. This applies only to INRD people, present or past. (Or the clearly impending future.) Exception: any RL information a person states about themself in a public space (like the lounge or a channel) with more than 3 other people listening is considered disclosed. (The discloser can subsequently revoke this by contacting each of those people and telling them so.)
No Willful Disruption[]
If you walk into the lounge and start spamming "DESU DESU DESU DESU" endlessly, so that nobody else can talk there, you might be punted to another room. If you page-spam people, they can ask you to stop, and you must comply. Speaking of which:
Right to Silence[]
People can ask you to stop paging them, @mailing them, or otherwise using a private avenue of communication to contact you. (This does not extend to public areas.) If they want, they can put a page-lock on as well.
Underage Creepiness[]
It's true that pedophilia and child abuse are significant issues in the modern world, and relevant to the setting. However, to avoid sketchiness, we're closing off these particular avenues. Any kind of underage sexual stuff needs to stay strictly off-screen (i.e. not roleplayed, not described), and mentioned (if at all) only very indirectly. Really, it's best to just omit it altogether, because it'll be more hassle than it's worth. It's necessary to avoid, well, creepiness.
There are plenty of other plotlines.
TinySex[]
Tribble shoes! Awwww. They're so teensy.
TinySex: the roleplaying of sexual activity. This is a most controversial subject. Yes, it's said that once upon a time, on a faraway MUX, two roleplayers TSed together and everything was totally IC, with the same honest character expression that typifies other kinds of good roleplay. It's believed that foreplay consisted of a playful chase on the backs of unicorns around a root beer waterfall. Unfortunately, policies often must be made with a mind for the average and the worst, not the best. And generally speaking, honest IC portrayal lasts in the heat of TS about as long as a hamster in a microwave. Just imagine the beeping sounds to remind yourself what you're doing to your poor characters.
TinySex is, however, not strictly banned at this time. We're not going to spy on any characters' bedrooms. Why? It's just too much hassle. And sure, people might need to portray brief snatches of TS as part of roleplay.
However, the official MUX solution is the fade to black. This is encouraged in lieu of TS. Really, some of the best usages of sexual activity in roleplay have been off-screen: it's usually the lead-up and the aftermath that matters. If things important to the story need to happen actually during sex, like an Impudite swiping some Essence, try a snippet in the middle.
If you're really got to RP Snuggliel and Sexargk doing it in graphic detail, please go make some Shang characters and do it there. Hey, they won't even have to make their Numinous Corpus rolls or spend Essence there!
Also, as though it needed to be said, TinySex involving minors is just not okay. (Yes, that covers non-minor celestials in the forms of underage humans, you sick perv.) No FTB, nothing.