Does anybody have any tips to keep a good stable relationship with the AIs? I feel the natural state of things is a vendetta with almost every other leader. They declare the vendetta almost every time I refuse any of their demands, no matter if I am military or tech leader. I have managed to get a Pact of Brotherhood with Corazón Santiago after accepting everything she wants from me, including intervening in her wars, but I fear as soon as I deny her a gift she will break it.

Additionally, do the social engineering policies I choose affect my relationship status with the AIs? Is there some kind of "trustworthiness/infamy tracker" so if I declare war (which I did to capture one base that the UN had shamelessly placed in my rightful territory) they are more likely to distrust me / consider me an enemy?

Also, since I know some games from this period used this trick: is there a bias against the human player?

Thanks in advance.

They're less likely to be hostile if you're substantially more powerful, but with Santiago or Godwinson even that isn't a guarantee. They also seem more likely to declare war if they're at a distance, and don't have as much to worry about in terms of immediate reprisal.
Your policies do make a difference, but what gets you on the good side of one faction is also going to get another one mad as hops for doing something so boneheaded. Most notably, policies that promote high Planet scores and environmental friendliness get you on good terms with Diedre and poor ones with Morgan, and vice versa.

In addition to what Paulon said, some factions are basically going to be hostile with each other or cold at best, no matter what you do.

For example, Miram is never going to get along with Zakharov. Miram moreso because she's a lunatic, but Zakharov would probably just laugh because he could subjugate her with technology.

I am indeed playing as Zakharov so I guess it's a lost cause with some of them. I will keep in mind your advice, thank you.

That's great advice, and similar to how it works in Civilization IV. I just wanted to be left alone teching as the University, so my initial plan was to refuse all the vendetta demands, but it didn't work as planned. Now Santiago is my Pact Sister so I guess that settles whose side I'm in.

Also, despite being in 2-3 vendettas at all times, the AIs don't seem too interested in attacking me (perhaps that's the relatively low difficulty level, or because I have now my own landmass and they are not very good at transoceanic invasions). So maybe I could try to complete the tech tree and build military units just for garrison duty,

That treacherous snake of Corazón Santiago betrayed me! She broke the Pact of Brotherhood and then declared vendetta (twice). She took two of my cities but I took six of hers, so I am only moderately mad.

I ended up destroying what little reputation I had left when I used planet busters, but I trascended, so who cares what they think of me. :D

Yes, your performance can contradict your policy, and friendly civilizations will adjust their perception/s.

If you are truthful, even if belligerent (which is the whole point of the game), then allies and foes will refer to you as such.

For example, if an ally asks to join battle against a third nation, they will offer up their battle plans as part of the briefing; if you have treacherously attacked any other group then the (potential or actual) ally will be less transparent and forthcoming.

Are there still players who think AI diplomacy has value in this game? hehehehe, that's cute.

What you are supposed to do, is simply enjoy what the game is trying to give you.... The true purpose of AI diplomacy is to give you reason to want revenge and then take great enjoyment out of killing everyone and that's it.

Even blood brother AI ram colonizers/cities up your arse, and why do you think that is in its programming? See above comment.

Well, well, I think the AI is nowhere that complex. It just stupidly search for great (well, 'great' in its flawed reasoning) spots to colonise, giving no f where it is and whom he offending doing it, then refuse to deal with consequences in a reasonable (humanly) way, again just because it's strigh forward simple, stupid and flawed.

Human perception and reasoning is way more complex than most realise, and includes irrational components almost impossible to model, although some of that can emerge in AI behaviour (at least when interpreted by highly imaginative human perception) with enough fuzzy logic.

Well, ok, if you must spoil my much more fun fuzzy logic..... yes of course the AI likes to put sea colonies next to forrest, and where is the forrest in this game? Where the player planted it for his own cities mostly! Then what happens when your former's try to raise terrain? Yea, Nah, and thats how the player comes to feel like he has been F-ed up the arse by a pact brother.

As long as your social engineering is set to survival mode, you can get along with the different factions, except Miriam and Yang which cannot be trusted anytime. It may be worth paying some tribute so they leave you alone and you can build up your army.
Morgan is likely to make you a pact if you want it and Deirdre has a tendency to be generous in the beginning.

I normally go for Democracy / Knowledge / Green asap. This will mean no issues with Deirdre or Profet Cha Dawn, nor with Zacharov or the conscienceness and it speeds up discovering new technologies. BUT it will make Santiago suspicious and also causes conflicts with Miriam and Yang and Morgan will somewhere mid-game declare war on you.

Secret projects: always go for the Human Genome project, the virtual world (good against drones and good for science). Trade secrets with all if you can except Yang and Miriam.

Tend for your reputation - if you really want war with someone, provoke him/her through diplomatic threats, so THEY declare war to you.

Develop sea bases as soon as you can (I play the Nautilus pirates often). Create a unit for defense, then sea formers, then an attack unit or something to save you for too many drones, depending the level you play. In the classic game, I usually play the Spartans - it takes a dangerous faction out of the game and I can still go for my social engineering goals.

Use probe teams to set up factions against one another and gain tech if you can. This is risky of course but worth the risk for essential inventions.

Develop a sturdy air force. There is nothing much that can stand up to it.

Go for the Ascend to Transcendence win... lots of points qnd I like the ending :-;

Thank you all for the tips. :)

In my experience, the biggest factors in relations with the other faction leaders are your social engineering policies and relative military strength. For example, if you're running Planned/Police State as Yang, Morgan will hate you unless you have overwhelming military strength. If you're running Democratic/Green/Knowledge as Commissioner Lal, Deidre and Zakharov will like you more than Yang and Morgan. If you have 50 planet busters as Santiago, nobody will mess with you.

The good old power of diplomation. ;)