How does diplomacy/reputation work

[Pantagruel]

I'm sure it has been done somewhere else, but could you give a thorough explanation to me how diplomacy works in this game? Reputation I mean. I like how there is a penalty for being a warmonger, but once, playing as the Cumans, I went from "mixed" (I think?) to "very untrustworthy" from occupying (!) two Georgian settlements, even though I had no sort of prior deal with them, not even trade rights. It isn't as important maybe when playing a steppe faction bent on conquest; but later I tried to play as the Sultanate of Rum, I was attacked early by the Byzantines, I defeated a raiding party of 5 regiments, and after asking for a simple ransom for the 35 or so soldiers that was captured, I went from "mixed" to "dubious". I want to like this mod, but I need to know the thinking behind this reputation system so I do not continue myself.

And another question, do you get penalty to reputation from occupying a rebel settlement?

[nein]

Diplomacy is largely broken in the earlier TW games, the only things you need to know about BC are that your faction affects your diplomacy, for example the Armenians can get a free alliance and trade rights with the crusaders as long as they don't sack anything beforehand (sacking is a nono until you secure those precious faction exclusive alliances/trade rights)... whilst some factions have enmity towards you aka the rum seljuks and romans, they cannot get an alliance or even trade rights with one another without paying out massively. Alliances in BC are fixed meaning that the AI cannot break them so they are very useful. Many factions will offer trade rights as long as you have no historical enmity even if you have terrible standing

[Pantagruel]

Thank you, that makes sense. I like it to make sense, but it did not earlier (to me, being accustomed to the regular Total War diplomacy). But my main beef is still reputation. Maybe it does not matter much. Going from 'mixed' to 'despicable' in two-three occupying of settlements gives me the shakes. But again, maybe it does not matter? In vanilla Total War reputation have plenty to say though, how willing other factions are to declare war on you, their willingness to accept trade, peace, etc.

[naq]

As a despicable Roman at the start of my campaign I cant make trade right with anyone except Kipchaks and Georgians.

[nein]

The koj, turks and armenians are hardcoded to hate you... still you can trade with the ayyubids which is somewhat useful for your coastal regions

[Geoffrey of Villehardouin]

A drop in reputation as the human player becomes stronger is practically necessary for the AI to remain aggressive.