Octodon:

no rules in particular, be nice be reasonable call me mommy stuff like that

Seriously though: It should be similar to mastodon.social.
NSFW/any legal porn is allowed, but tag it as NSFW or make it unlisted or less. Trolls are only allowed if they're quiet; you can shitpost but not harass someone, and my threshold is pretty low. I'm not Twitter, I'll fuck up nazis and bullies for fun, and get an AI to do it if I get bored.
I'm your nice cyberpunk queen and I intend to keep this place decent and safe for everyone.

You should choose an instance based on shared values; here I believe everyone deserves freedom, but also to be safe from harassment and hate. An abstract notion of asymmetrical freedom will not be given a higher priority - freedom of speech doesn't mean you are immune to any liability for your actions.

I'll always try to solve problems in the most rational and safe way possible for users, and try to discuss any issue with the people concerned if I think it's worth it. If you at least try to be good and comprehensive, so will I. I understand and accept mistakes, but not being bad on purpose.

Advertising: Probably never, if any it will not be integrated into content or intrusive, at most I'm thinking about the Wikipedia way of asking for donation when needed.

Federation & Politics: It federates with nearly everything, I'll silence or block whatever instance isn't compatible with this site's rules as needed. (silence: anyone can follow anyone, but toots will be hidden by default) For example when a remote user harasses a local user or sends spam, their instance admins will be notified; if they find such behavior acceptable and tolerate it, the instance may get silenced to prevent likely future issues. The list is published at the end of this page.
Anyone complaining: that's a private place and your free speech means very little to me and most of my users. If your instance gets blocked it's because you endorse hate and/or harassment; then why be pathetic now and whine about it? You can't force people to like you and being an asshole won't make us friends. Go run your little world.

CW: On public toots (not unlisted, private, or direct), content warnings are required for any kind of (explicit enough) violence (with or without pics, including gore, *phobia, abuse, sexual or not) and referring to it; sexual content (pics must already be tagged as NSFW, use a CW if you have text or want to warn about specific content).
This is not about what is culturally or religiously accepted, but about common sources of trauma that deeply hurt people for very real reasons. Consider yourself lucky if you don't need any of it, but it's about others.
They are also appreciated but not mandatory on: politics, spoilers, anything depressing or too negative. Use them in an opportunistic way.

Enforcement: On this instance, a toot that doesn't follow these rules may be deleted. On repeated offences or if disturbing public timelines, the account may get silenced (only their followers will see toots). If silencing is not enough (harassment, ...), the account may get completely suspended.
If the account is on another instance, it may get silenced and suspended from here, and I will not hesitate to share reports with other instance admins.
Instance admins, feel free to contact me about this instance's users' behavior.

Privacy: As people bring up the issue regularly with Mastodon, I can technically read your DMs or private statuses. So does Twitter on Twitter, Google on GMail, IRC operators on the text sent over their servers, and any other service that doesn't encrypt the content end-to-end. However: 1. I will not do so unless i have a serious and justifiable reason (like a report sent by the other person involved in a DM), and I will in any case respect your privacy unless someone or the instance's safety is at risk. 2. If secrecy is paramount, you are allowed and encouraged to encrypt your DMs (or any other status) by any mean available that is preferably out of my control, so that I simply can't be asked to read it.

Support / Servers: You can support me/this instance through a Patreon here or on Liberapay and you can get a VPN here or send bitcoins to 18NY191tpG3WhvRbjxxcqHG4MFgCkSSsAA.

If you're wondering, it's hosted in France.
Feel free to report it to me directly if it's slow or anything doesn't work.

Silenced instances:

sealion.club, heldscal.la, freezepeach.xyz, shitposter.club, anime.website, unsafe.space, (gs|pl).smuglo.li, anitwitter.moe, npf.mlpol.net, toot.love, kyot.me, mastodon.blue, noagendasocial.com, toot.zone, waifu.social, freespeech.firedragonstudios.com, are silenced or suspended as they tolerate hate speech or harassment from their users or participate in such things.

baraag.net as they host lolicon (among others, but that's the legally edgy part).