Couldn’t find if this has already been mentioned, but you can still trade with factions you are at war with at -100 diplomacy. Seems more like a bug than a ‘feature’.
the opinion of the haven also matters. If the haven doesn’t hate you, they will still trade with you
Seems a bit weird if you are at war. I noticed I did have a positive standing with some of those havens so that could be it.
it should be that if your at war with a faction: either they won’t trade with or the faction gives you a let say 50% increase in exchange of resources.
maybe a discount and increase in exchange base on your diplomatic status with the faction.
allied= 50-75% discount
alligned= 20-40% discount
supportive= 10% discount
neutral= 0% discount
unfriendly= 20-30% increase
hostile= 40-50% increase
at war= 70-80% increase